Betty and Gabby collected stamps. Betty gave 30% of her stamps to Gabby and as a result, Gabby's stamps increased by 25%. If Betty had 70 stamps left, find the number of stamps Gabby should give to Betty in the end so that both had an equal number of stamps.

	Betty	Gabby	Comparing the change in Gabby's stamps
Before	10x1 = 10 u		4x3 = 12u
Change	- 3x1 = - 3 u	+ 3x1 = + 3 u	+ 1x3 = + 3 u
After	7x1 = 7 u		5x3 = 15 u

30% = ³⁰₁₀₀ = ³₁₀
25% = ²⁵₁₀₀ = ¹₄

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

7 u = 70

1 u = 70 ÷ 7 = 10

Number of stamps that Gabby had more than Betty in the end
= 15 u - 7 u
= 8 u

Number of stamps that Gabby should give to Betty so that both had an equal number of stamps in the end
= 8 u ÷ 2
= 4 u
= 4 x 10
= 40

Answer(s): 40