In January, Flynn gave his wife, Cathy, $4000 for household expenditure. Cathy spent 70% of the sum on rental, 10% on food and saved the rest. In February, Flynn reduced the sum he gave to Cathy. Cathy spent the same amount on rental and reduced the amount she spent on food by 20%. She saved the remaining 20% of the sum given to her in February. By what percentage was the sum given to Cathy reduced by?

	Rental	Food	Savings	Total
Before	70%	10%	20%	$4000
Change		- 2%	- ?	- ?
After	70%	8%
Comparing the amounts spent in February	80 u		20 u	100 u

Amount that Flynn saved in percent
= 100% - 70% - 10%
= 20%

Amount that Flynn reduced on food in percent
= 20% x 10%
= ²⁰₁₀₀ x 10
= 2%

Total amount that Flynn spent on rental and food in percent
= 70% + 8%
= 78%

100% → 4000

1% → 4000 ÷ 100 = 40

78% → 78 x  40 = 3120

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

80 u = 78% 

80 u = 3120

1 u = 3120 ÷ 80 = 39

Amount that Flynn gave to Cathy in February
= 100 u
= 100 x 39
= $3900

Amount that Cathy received less from Flynn from January to February
= 4000 - 3900
= $100

Percentage that the sum given to Cathy was reduced by from January to February
= ¹⁰⁰₄₀₀₀ x 100%
= 2.5%

Answer(s): 2.5%