Pamela and Cathy collected cards. Pamela gave 50% of her cards to Cathy and as a result, Cathy's cards increased by 30%. If Pamela had 21 cards left, find the number of cards Cathy should give to Pamela in the end so that both had an equal number of cards.

	Pamela	Cathy	Comparing the change in Cathy's cards
Before	2x3 = 6 u		10x1 = 10u
Change	- 1x3 = - 3 u	+ 1x3 = + 3 u	+ 3x1 = + 3 u
After	1x3 = 3 u		13x1 = 13 u

50% = ⁵⁰₁₀₀ = ¹₂
30% = ³⁰₁₀₀ = ³₁₀

The increase in the number of cards that Cathy had is repeated.  Make the increase in the number of cards that Cathy had the same. LCM of 1 and 3 = 3

3 u = 21

1 u = 21 ÷ 3 = 7

Number of cards that Cathy had more than Pamela in the end
= 13 u - 3 u
= 10 u

Number of cards that Cathy should give to Pamela so that both had an equal number of cards in the end
= 10 u ÷ 2
= 5 u
= 5 x 7
= 35

Answer(s): 35