PSLE
Lynn and John bought storybooks at the prices shown below.

3 Large storybooks for $15
5 Small storybooks for $9

1. Lynn bought an equal number of large and small storybooks. She spent $96 more on the large ones. How many storybooks did she buy altogether?
2. John spent an equal amount of money on the large and small storybooks. What fraction of the storybooks he bought were large?

(a)
Number of large and small storybooks that Lynn bought is the same. Make the number of large and small storybooks the same. LCM of 3 and 5 is 15.

Cost of 3 large storybooks = $15
Cost of 15 large storybooks = 5 x 15 = $75

Cost of 5 small storybooks = $9
Cost of 15 small storybooks = 3 x 9 = $27

Difference in the cost of buying 15 small storybooks and 15 large storybooks
= 75 - 27
= $48

Number of sets of storybooks
= 96 ÷ 48
= 2

Number of storybooks that Lynn bought
= 2 x 2 x 15
= 60

(b)
John spent an equal amount of money on the large and small storybooks.  Make the amount of money spent on the large and small storybooks the same.
LCM of 15 and 9 is 45.

Number of large storybooks that John bought
= 3 x (45 ÷ 15)
= 3 x 3
= 9

Number of the small storybooks that John bought
= 5 x (45 ÷ 9)
= 5 x 5
= 25

Fraction of the storybooks that John bought that were large
= ⁹_{9 + 25}
= ⁹₃₄

Answer(s): (a) 60; (b) ⁹₃₄