A car travels 20% faster than a truck, if the car’s speed is 80 mph, what’s the truck’s speed? 

Not in a lot of the US. I've driven roads in Texas, posted 100 mph, and in northern Michigan it's 75. A cop won't even look twice at 80 in a 75.

on Route 66

Wow you get $100's to count? 😀

You win!!!!

No, the difference, or how much faster, is 20% of the truck speed, which is less than car speed of 80 mph. This 20% is therefore less than 16.

@@Serisky621 As I said " that is why people are saying 64." I didn't say anything about wrong or right.

Which gives you the wrong answer

@@sudsfour4553 You obviously didn't follow the conversation. The question many were asking is why so many people were saying 64. Start with the video and follow the comments.

Bingo

NONSENSE!! the car speed IS NOT = 120%(100truck +20 car)...how the hell did you arrive at that????.The car speed IS 80mph and you have to work WITH THAT,IT HAS NOTHING TO DO with PERCENTAGES...it IS 80 mph and who says the TRUCKS speed is 100%? how do you know that?that is saying that the TRUCK is MOVING AT ITS MAXIMEM SPEED and in the CARS' case,you are telling yourself that the CAR is moving at its MAXIMUM SPEED PLUS another 20% above its MAXIMUM speed...IMPOSSIBLE !! You STARTED WRONG so YOU had to END WRONG.

​@@michaelaustin-xx7cuThey didn't "arrive at" car speed = 120% of truck speed. The question literally says that. It's right there at the start of the video, in plain English. I had originally thought that your issue was understanding how percentages work, but I wonder if it's an English comprehension problem.

@@gavindeane3670 WHERE ??? show me !!.I had originally thought that your issue was understanding how percentages work, but I wonder if it's an English comprehension problem.

​@@michaelaustin-xx7cu"A car travels 20% faster than a truck" literally means that the car's speed is 120% of the truck's speed (which is just another way of saying that the car's speed equals the truck's speed × 1.2). Do you understand that?

YOU don't have to do all of that.20% of 80 is 16,then take it away from 80 because the Truck is moving SLOWER and you get 64mph

​@@michaelaustin-xx7cuAnd you get the wrong answer.

@Pax.Alotin : 75% of nothing is nothing.

The result would be much less than original number, if original is positive. For example, 100 + 50% =150 150 - 50% = 75

You will get to where you’re going first because I will be pulled over getting a ticket!😂

"A truck travels 20% slower than a car" is not the same as "A car travels 20% faster than a truck". In the first case, the difference in speeds is 0.2 × the car's speed. In the second case (which is what the video asks) the difference in speeds is 0.2 × the truck's speed.

Got it wrong

CORRECT!! don't know why people are using the 20% on the TRUCKS' speed since the TRUCKS' speed is the one that was ASKED for

​@@michaelaustin-xx7cuPercentages don't work like that! If you take some value (like the car's speed in this case) and you reduce that value by 20%, then you take that reduced figure and increase it by 20%, you do not get back to where you started. If the truck is doing 64mph then the car is doing 25% more than the truck's speed not 20% more than the truck's speed.

You answered it in your head but you answered a completely different question. You answered "A truck travels 20% slower than a car". That's not the same as "A car travels 20% faster than a truck". That's not how percentages work.

@@gavindeane3670 ...and I know that,but what is your point?

​@@michaelaustin-xx7cuMy point is that "20% faster than the truck" and "20% slower than the car" are not the same thing. You seem to think they are. 64 is 20% less than 80, but 80 is not 20% more than 64. It's very obvious that 64mph is not the answer here. If the car is doing 80mph and the truck is doing 64mph then the car is not traveling 20% faster than the truck, is it. The car is traveling 25% faster than the truck.

But if the truck is going 64 then 20% faster is 76.8 mph which is not 80 mph. The answer is approximately 66.666666 repeating.

​You fell into a common math trap. The difference in speed is 20% of smaller (truck) speed, NOT 20% of larger (car) speed.

I asked the SAME question

And, still no answer!

When you think you've got an answer, it's always a good idea to check your answer. As he shows in the video, when a truck is doing 64mph, then something going 20% faster than that truck is doing 76.8mph. Given that 76.8mph is NOT the spec of our car in the question, we have established that we must have gone wrong somewhere when calculating the truck's speed as 64mph. That's the entire point of checking your answer - to confirm whether it's correct or not. That's only half the battle of course. Having established that you've got the answer wrong, it's then a case of whether you can figure out WHERE you went wrong.

Don't brag!

that's what you get when you incorrectly subtract 20% of 80

66.666

The truck's speed is 100% of the truck's speed. Let's call that x The car's speed, 80 mph, is x plus 20% of x. Which makes the car's speed 120% of x. That's why 80 isn't the 100% figure.

EXACTLY !! and that is the SAME way I used it and got 64mph.

My argument is if 20% of 80 mph represents how fast the CAR is travelling then the REMAINING 80% represents how fast the CAR is travelling at the SLOWER or NORMAL speed and the truck is travelling at the SLOWER or NORMAL speed which is 80% of 80 which is 64mph,furthermore 100% of 80 is 80,but those who are coming up with 66.7 are using 100 as the 100% figure and adding another 20%,when as you asked the IMPORTANT question " why can't 80 be the 100% figure".NOTE !! they NEVER made use of the remaining 80%.When I asked a certain person here to tell me what is WRONG with my reasoning all they did AGAIN was to show their 120% Cars speed = 100T=20% equation to show my 64mph was wrong, when it is obvious it couldn't have been right because they were using their EQUATION and not mine which is CARS speed ( % )= 80% SLOWER speed+20% FASTER speed and if you work backwards EVERYTHING ADDS UP......80% of 80mph=64 and 20% of 80mph=16....and 64 +16 = 80

It took me far too long to get this joke.

I like your style straight to the point

You formulated better than his original question,he makes you concentrate on the cars speed.

Where did you get the 1.20 from? I can’t see the original problem now. Is that supposed to represent 20%?

@@martinbrenner6664 the car is traveling 1.2 times or 120% faster than the truck.

Thanks, I just never saw it represented in that way before, I just wanted to make sure.👍🏻

You've answered "a truck travels 20% slower than a car". That's a different question.

Wrong

​@@Sam2shamNo, wrong. They've answered "a truck travels 20% slower than a car", which is a different question.

@@mikeorgan1993 RIGHT

Jesus wept over the number of people who answered, "64."

No, 20% more than the truck.

Because "a truck travels 20% slower than a car" is not the same as "a car travels 20% faster than a truck". In the first case, the difference in speeds is 20% of the car's speed. In the second case (which is what the question asks here) the difference in speeds is 20% of the truck's speed.

It is the correct answer, the .7 is rounded, really it's 66.666666 with the 6's repeating forever and with each 6, it is closer to 66.7, 66.7 is just an approximation

Exactly !! it says 80 and NOT 80 point something,yet some people are coming up with a DECIMAL in their answer....HOW ????

@@eatyourpants3947 You don't UNDERSTAND what DarrenBarstad is saying

@@michaelaustin-xx7cu No, I do. I don't think you understand what I'm saying. The answer is 66.7 because it's an approximation; not the exact answer. We can not put the EXACT answer because it is simply impossible to write as a decimal. You can write it as 200/3 for the exact value, but we approximated the value for it so we could write it as a decimal, 66.6666 (repeating forever), which is approx 66.7.

@@eatyourpants3947 ...but you seem not to understand what DarrenBarstad and I are saying...look the cars' speed is 80mph which is DEVOID of any DECIMAL POINT,therefore, how can you come up with an answer for the Trucks speed WITH A DECIMAL POINT?so OBVIOUSLY that answer CANNOT be the CORRECT ONE.

That's not how percentages work. The truck is traveling at 83⅓% of the speed of the car.

The car is 20% faster than the truck. 80 mph ( the car ) is 20% faster than 66.66 mph ( the truck ). You need to compute 20% more than the truck's speed because that is how the question is worded. He never said ... The truck was 20% slower than the car = a completely different calculation.

​@@MrSummitvilleExactly. The start of the question, "a car travels 20% faster than a truck", immediately gives us the equation C = 1.2 × T Failing to get that equation requires either failing in basic English comprehension or failing in an elementary understanding of percentages. From that equation it is obvious that given the speed of one of the vehicles we can determine the speed of the other. And that is exactly what the remainder of the question does: gives one speed and asks for the other.

Hum, guess maybe there someplace where the posted legal speed is 85mph. Another vote for Biden just goes further in assuring us you have your head where it can’t see.

If Biden is reelected, that will probably destroy our country, G-d forbid!!!

I’m the same way. I did X + 1/5X = 80. Then multiplied both sides by 5 getting 6X=400. Then divide both sides by 6 getting X=66.67

CORRECT !!

So how are you making use of the 20% of the 80mph? because if 20% of 80 is 16 and the Trucks' speed is 64 the car is going at 80mph.

​@@michaelaustin-xx7cuThey are making use of the 20% in exactly the way the question tells them to. We aren't told the truck's speed. But we are told that whatever the truck's speed is, if you multiply it by 1.2 then you will get the car's speed. And since we know the car's speed, it is simple to deduce what the truck's speed must be. The truck's speed equals the car 's speed divided by 1.2.

...because the QUESTION says that AT THE SPEED of the CAR which is 80mph,it is moving 20% faster than the TRUCK..the writer is saying that cars in general usually travel 20% faster than trucks and at that speed ( 80mph ) what is the trucks' speed.Furthermore,how can you jump from 80mph to 100% and then add the 20% to the cars' speed and call it 120 %? if you are using % then,100% of 80mph means that the car is travelling at 160 mph

​​​@@michaelaustin-xx7cuNobody is adding anything to the car's speed. Where do you get that from??? The speed of the car equals 100% of the truck's speed plus a further 20% of the truck's speed. Very simply, using C for the car's speed and T for the truck's speed, we are told that C = 1.2×T and then we are asked to find the value of T given C=80mph. When I first read some of your comments, it seemed like your misunderstanding was simply that you thought the equation here was T = 0.8×C, but now it seems like your misunderstanding is not that simple and there's more to it.

@@gavindeane3670 NO !! you have it all wrong...the speed of the CAR equals the speed of the truck plus 20% of the CARS' Speed Speed of TRUCK is 64 and 20% of 80 is 16....64+16= 80

I'm glad you are not my math teacher. I would totally fail if I relied on your advice. Don't need to hurt your feelings but you complicate the simple.

​@@davenoejoeyou must return to elementary school. The guy is right

The only one right

You've done "A truck travels 20% slower than a car". That's a different question, as you can see from the fact that in your solution the car is traveling 25% faster than the truck, not 20% faster.

EXACTLY !!...based on the TWO KNOWN NUMBERS

@@gavindeane3670 - how did you calculate my equation to arrive at 25% faster then the truck? Doesn’t 25% of 80 = 20? 20x4 = 80, 1/4th is 25% of something isn’t it? In my theoretical calculation, 20% of 80 = 16, not 20. If an object is traveling 20% slower then an object traveling at 80 mph, doesn’t it stand to reason, given the known speed of 80 MPH or 80, and the 2nd known number of 20% slower or 20%, that 16 is 20% of 80. If the object is 20% less (or 16MPH) then 80, 16 - 80 = 64. But I’m not a rocket scientist…

​@@Patriot_Drone_ServicesHow did I arrive at 25% faster than the truck? Simple. You said the truck was doing 64mph. 25% of 64 is 16. So if the truck is doing 64mph then something going 25% faster than the truck would be doing 64 + 16 = 80mph. But since we know that the car in the question is doing 80mph, and we know that the car is going 20% faster than the truck, not 25% faster than the truck, we can immediately see that the truck's speed cannot be 64mph. You keep taking about the truck being 20% slower than the car but that's not what the question says. The question says the car is going 20% faster than the truck. Your answer would be correct if the question was: "A truck is traveling 20% slower than a car. If the car's speed is 80mph, what is the truck's speed?", but that is a different question.

@@gavindeane3670 that’s why I’m not a rocket scientist

That is how we were taught to set up the formula in school. The "new math" rules my daughters came home with made me wonder why in the world would they complicate something that is already complicated to most people.

I wish I could do mental arithmetic like this

@taylormatthews3767 First of all, read the question carefully. Sometimes it helps to say it out loud. It provides aural feedback that reinforces the brain's internal ones. Then, analyse the question. In this case, start by considering what the first sentence means. 20% faster means that the car is travelling at the truck's speed plus 0.2 times the truck's speed. So that is therefore 1.2 times the truck's speed. Now we need some basic algebra. Let's call the truck's speed T. 80 = T × 1.2 Therefore, 80 ÷ 1.2 = T You can now divide 80 by 1.2 to get the truck's speed. But there's a quicker way. Both 80 and 1.2 are divisible by 4. So, doing that, you finish up with 20 ÷ 0.3. Now, 20 ÷ 3 is 6 remainder 2, so that's 6.666.... But, 3 is 10 times greater than 0.3, so you need to multiply 6.666.... by 10, giving us 66.6666... mph. Final check- does 66.666mph make sense? Yes it does. I'm good at mathematics, but I'm useless at teaching. Too impatient. But that's how my mind worked on this problem I find that mental arithmetic works better for me if I visualise the actual numbers and equations in my mind. I close my eyes and see "80", for instance. We all have our own talents. Mine is boredom, but your's are probably much more interesting.

Your words...... which are OBVIOUSLY WRONG....."Therefore, 80 ÷ 1.2 = T You can now divide 80 by 1.2 to get the truck's speed".Big man if you divide 80 by 1.2 you would get 96 and that would be saying that the TRUCK was travelling faster than the car.

​@@michaelaustin-xx7cuIf you MULTIPLY 80 by 1.2 you would get 96. But nobody is suggesting that. If you DIVIDE 80 by 1.2 you get 66⅔.

Your method is the CORRECT method in my opinion but 20% of 80 is actually 16,so the trucks' speed is 64 mph and I too don't know where the 100% faster plus 20 % comes from....

Where does car speed = 120% of truck's speed come from? It's right there in the question. "A truck travels 20% slower than a car" is not the same as "a car travels 20% faster than a truck".

@@gavindeane3670 Where ????show me.Are you telling yourself that a car can travel at its MAXIMUM PLUS 20% MORE?????

...your mistake is that T is not 1.2 it is 1 since T is NOT 100% it is 80% and that is .8 + .2=1 or 80/1 which is the TRUCKS speed 80mph which is ALSO the CARS NORMAL SPEED,but seeing that at that speed the car is travelling 20% FASTER,the obvious thing is to subtract 20% of 80mph to get the Trucks speed...OR you could have gone direct and taken 80% of 80mph and get the same result which is 64.Using my equation Cars' speed ( 100%)=Normal speed +Faster speed or 80% Normal speed+ 20% faster speed,where 80% of 80 is the Trucks speed which again works out to be 64mph OR you could have taken 16 mph from the known speed of 80mph.... and if you add the 20%to the trucks speed you get back the cars speed....but those of you that are getting 66.666667 are COMPLETELY IGNORING the REMAINING 80% and instead calling it 100%

@@michaelaustin-xx7cu the Car travelling 20% faster than the Truck is not the same as the Truck travelling at 80% the speed of the Car.

@@isilas476 Says WHO? so are you therefore saying that the Car travelling 20% faster than the Truck is the same as the Truck travelling at 100% the speed of the Car?

...and using your line of thinking isn't 100% of 80% not 80 % ?

​@@michaelaustin-xx7cuSays who? Says literally everybody who understands English and unstable how percentages work. This seems to keep coming back to the fundamental problem of you not understanding that "a car travels 20% faster than a truck" and "a truck travels 20% slower than a car" do not mean the same thing.

?????

@@michaelaustin-xx7cu 2 + 2 x 2 = ?

80 mph, 20 percent less 80 mph, 80% ÷ 100% × 80 mph = 64 mph.

82.5 ÷ 100 × 80 mph = 66 mph 17.5% less

You are answering "a truck travels 20% slower than a car". That's a different question. For the question in the video, the difference in speeds is 20% of the truck's speed, but you've solved it such that the difference is 20% of the car's speed.

We know it's 20% of the truck's speed. All the information you need is right there in the question. The car's speed is expressed in terms of the truck's speed.

@@gavindeane3670 I suppose I meant it's a common mistake 4/5 v 5/6. Agreed the information is there.