In November, Seth gave his wife, Cathy, $8000 for household expenditure. Cathy spent 50% of the sum on rental, 20% on food and saved the rest. In December, Seth 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 December. By what percentage was the sum given to Cathy reduced by?

	Rental	Food	Savings	Total
Before	50%	20%	30%	$8000
Change		- 4%	- ?	- ?
After	50%	16%
Comparing the amounts spent in December	80 u		20 u	100 u

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

Amount that Seth reduced on food in percent
= 20% x 20%
= ²⁰₁₀₀ x 20
= 4%

Total amount that Seth spent on rental and food in percent
= 50% + 16%
= 66%

100% → 8000

1% → 8000 ÷ 100 = 80

66% → 66 x  80 = 5280

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

80 u = 66% 

80 u = 5280

1 u = 5280 ÷ 80 = 66

Amount that Seth gave to Cathy in December
= 100 u
= 100 x 66
= $6600

Amount that Cathy received less from Seth from November to December
= 8000 - 6600
= $1400

Percentage that the sum given to Cathy was reduced by from November to December
= ¹⁴⁰⁰₈₀₀₀ x 100%
= 17.5%

Answer(s): 17.5%