PSLE
Risa and Dana folded paper balls over two days. On Saturday, Risa folded 21 paper balls more than Dana. On Sunday, Risa folded another 35 paper balls and Dana folded another 16. At the end of the two days, Risa made ⁷₁₀ of the total number of balls. What was the number of paper balls that Dana folded?

	Risa	Dana	Difference
Before	1 u + 21	1 u	21
Change	+ 35	+ 16
After	1 u + 56	1 u + 16	40
Comparing between Risa and Dana in the end	7 p	3 p	4 p

Difference between the number of paper balls that Risa and Dana folded in the end is repeated.

Difference between the number of paper balls that Risa and Dana folded in the end
= 7 p - 3 p
= 4 p

Difference between the number of paper balls that Risa and Dana folded in the end
= (1 u + 56) - (1 u + 16)
= 1 u + 56 - 1 u - 16
= 56 - 16
= 40

4 p = 40

1 p = 40 ÷ 4 = 10

Number of paper balls that Dana folded
= 3 p
= 3 x 10
= 30

Answer(s): 30