Opal and Vanessa collected postcards. Opal gave 50% of her postcards to Vanessa and as a result, Vanessa's postcards increased by 30%. If Opal had 27 postcards left, find the number of postcards Vanessa should give to Opal in the end so that both had an equal number of postcards.

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

3 u = 27

1 u = 27 ÷ 3 = 9

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

Number of postcards that Vanessa should give to Opal so that both had an equal number of postcards in the end
= 10 u ÷ 2
= 5 u
= 5 x 9
= 45

Answer(s): 45