Hi im stuck on 3 questions from my maths txt book.

questions 7,11, and 12

http://img527.imageshack.us/img527/772/dsc00663zz8.jpg

answers are

7: 0.41

11: 0.94

12: 0.92

my answer for 7 comes up as 5.75, 11 and 12 are off aswell.

thx in advance all help is appreciated.