In February, Peter gave his wife, Penelope, $4000 for household expenditure. Penelope spent 50% of the sum on rental, 20% on food and saved the rest. In March, Peter reduced the sum he gave to Penelope. Penelope spent the same amount on rental and reduced the amount she spent on food by 10%. She saved the remaining 20% of the sum given to her in March. By what percentage was the sum given to Penelope reduced by?

	Rental	Food	Savings	Total
Before	50%	20%	30%	$4000
Change		- 2%	- ?	- ?
After	50%	18%
Comparing the amounts spent in March	80 u		20 u	100 u

Amount that Peter saved in percent
= 100% - 50% - 20%
= 30%

Amount that Peter reduced on food in percent
= 10% x 20%
= ¹⁰₁₀₀ x 20
= 2%

Total amount that Peter spent on rental and food in percent
= 50% + 18%
= 68%

100% → 4000

1% → 4000 ÷ 100 = 40

68% → 68 x  40 = 2720

The total amount that Peter spent on rental and food is repeated. 

80 u = 68% 

80 u = 2720

1 u = 2720 ÷ 80 = 34

Amount that Peter gave to Penelope in March
= 100 u
= 100 x 34
= $3400

Amount that Penelope received less from Peter from February to March
= 4000 - 3400
= $600

Percentage that the sum given to Penelope was reduced by from February to March
= ⁶⁰⁰₄₀₀₀ x 100%
= 15%

Answer(s): 15%