Wednesday, June 8, 2011

Trial and error 2

There are 40 students going to the library. each girl borrowed 5 books and each boy borrowed 3 books. The girls have 128 more books than boys. How many girls are there ? 

Let all students be girls 

40 x 5 = 200 books 

Difference= 200-128 = 72

Sum of each = 5+3 =8

72/8= 9 boys

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