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

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

3 u = 21

1 u = 21 ÷ 3 = 7

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

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

Answer(s): 35