Betty and Penelope collected cards. Betty gave 50% of her cards to Penelope and as a result, Penelope's cards increased by 30%. If Betty had 15 cards left, find the number of cards Penelope should give to Betty in the end so that both had an equal number of cards.

	Betty	Penelope	Comparing the change in Penelope'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 Penelope had is repeated.  Make the increase in the number of cards that Penelope had the same. LCM of 1 and 3 = 3

3 u = 15

1 u = 15 ÷ 3 = 5

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

Number of cards that Penelope should give to Betty so that both had an equal number of cards in the end
= 10 u ÷ 2
= 5 u
= 5 x 5
= 25

Answer(s): 25