PSLE
Gwen and Riordan bought jigsaw puzzles at the prices shown below.

2 Large jigsaw puzzles for $15
3 Small jigsaw puzzles for $10

1. Gwen bought an equal number of large and small jigsaw puzzles. She spent $100 more on the large ones. How many jigsaw puzzles did she buy altogether?
2. Riordan spent an equal amount of money on the large and small jigsaw puzzles. What fraction of the jigsaw puzzles he bought were large?

(a)
Number of large and small jigsaw puzzles that Gwen bought is the same. Make the number of large and small jigsaw puzzles the same. LCM of 2 and 3 is 6.

Cost of 2 large jigsaw puzzles = $15
Cost of 6 large jigsaw puzzles = 3 x 15 = $45

Cost of 3 small jigsaw puzzles = $10
Cost of 6 small jigsaw puzzles = 2 x 10 = $20

Difference in the cost of buying 6 small jigsaw puzzles and 6 large jigsaw puzzles
= 45 - 20
= $25

Number of sets of jigsaw puzzles
= 100 ÷ 25
= 4

Number of jigsaw puzzles that Gwen bought
= 4 x 2 x 6
= 48

(b)
Riordan spent an equal amount of money on the large and small jigsaw puzzles.  Make the amount of money spent on the large and small jigsaw puzzles the same.
LCM of 15 and 10 is 30.

Number of large jigsaw puzzles that Riordan bought
= 2 x (30 ÷ 15)
= 2 x 2
= 4

Number of the small jigsaw puzzles that Riordan bought
= 3 x (30 ÷ 10)
= 3 x 3
= 9

Fraction of the jigsaw puzzles that Riordan bought that were large
= ⁴_{4 + 9}
= ⁴₁₃

Answer(s): (a) 48; (b) ⁴₁₃