Zara has 30% as many stamps as Betty. Betty has 140% as many stamps as Nora. If Betty gives 50 stamps to Nora, both will then have an equal number of stamps. Find the average number of stamps the three of them have.

Zara	Betty	Nora
3x7	10x7
	7x10	5x10
21 u	70 u	50 u

30% = ³⁰₁₀₀ = ³₁₀
140% = ¹⁴⁰₁₀₀= ⁷₅

The number of stamps that Zara has is repeated.  Make the number of stamps that Zara has the same. LCM of 10 and 7 is 70.

	Betty	Nora	Total
Before	70 u	50 u	120 u
Change	- 10 u	+ 10 u
After	60 u	60 u	120 u

Total number of stamps that Betty and Nora have
= 70 u + 50 u
= 120 u

After Betty gives to Nora, both of them will have the same number of stamps. 

The total number of stamps that Betty and Nora have remains unchanged.

Number of stamps that each of them will have
= 120 u ÷ 2
= 60 u

Number of stamps that Betty gives to Nora
= 70 u - 60 u
= 10 u

10 u = 50

1 u = 50 ÷ 10 = 5

Total number of stamps that three of them have
= 120 u + 21 u
= 141 u

Average number of stamps that each of them have
= 141 u ÷ 3
= 47 u
= 47 x 5
= 235

Answer(s): 235