Here is a video of the last 5 rounds of show 5 of me on Countdown in November 2005. The aim of the game is to make the longest words using the letters given, or to make the target number using the given numbers once only.
The simplest way to get 286 seems to me to be the following way (and the two large numbers do help): 10 x 7 = 70 100 / 25 = 4 70 x 4 = 280 280 + 6 = 286 An alternative using all the numbers is: 25 x 7 = 175 175 + 100 = 275 10 / 2 = 5 275 + 6 + 5 = 286