David had some banana wafers and cranberry wafers. He gave away 100 wafers to his brother. 20% of them were banana wafers and the rest were cranberry wafers.

1. How many cranberry wafers did he give his brother?
2. David gave some banana wafers to his sister. ³₇ of all the wafers he gave away to his brother and his sister were banana wafers. How many banana wafers did he give his sister?

(a)
Percentage of cranberry wafers
= 100% - 20%
= 80%

Number of cranberry wafers that David gave to his brother
= 80% x 100
= ⁸⁰₁₀₀ x 100
= 80 

(b)
Fraction of all the wafers he gave away to his brother and his sister that were cranberry wafers
= 1 - ³₇
= ⁴₇

4 u = 80

1 u = 80 ÷ 4 = 20

Number of banana wafers that David gave to his brother and his sister
= 3 u
= 3 x 20
= 60

Number of banana wafers that David gave to his brother
= 100 - 80
= 20

Number of banana wafers that David gave to his sister
= 60 - 20
= 40

Answer(s): (a) 80; (b) 40