PSLE
Winnie and Rael bought storybooks at the prices shown below.

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

1. Winnie bought an equal number of large and small storybooks. She spent $117 more on the large ones. How many storybooks did she buy altogether?
2. Rael spent an equal amount of money on the large and small storybooks. What fraction of the storybooks he bought were small?

(a)
Number of large and small storybooks that Winnie bought is the same. Make the number of large and small storybooks the same. LCM of 4 and 5 is 20.

Cost of 4 large storybooks = $15
Cost of 20 large storybooks = 5 x 15 = $75

Cost of 5 small storybooks = $9
Cost of 20 small storybooks = 4 x 9 = $36

Difference in the cost of buying 20 small storybooks and 20 large storybooks
= 75 - 36
= $39

Number of sets of storybooks
= 117 ÷ 39
= 3

Number of storybooks that Winnie bought
= 3 x 2 x 20
= 120

(b)
Rael 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 Rael bought
= 4 x (45 ÷ 15)
= 4 x 3
= 12

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

Fraction of the storybooks that Rael bought that were small
= ²⁵_{12 + 25}
= ²⁵₃₇

Answer(s): (a) 120; (b) ²⁵₃₇