The approximate percent of average income used to pay federal, state, and local taxes is given by , where is the number of years after 1950. The actual tax load for 1970 was 31.4%. What does the formula give as an approximation? Round your answer to one decimal place.
A)21.0%
B)38.2%
C)30.9%
D)11.3%
E)33.6%

Question

The approximate percent  of average income used to pay federal, state, and local taxes is given by  , where  is the number of years after 1950. The actual tax load for 1970 was 31.4%. What does the formula give as an approximation? Round your answer to one decimal place. ​
A)21.0% 
B)38.2% 
C)30.9% 
D)11.3% 
E)33.6%

Quizplus · Accepted Answer

Plug in 1970 (20 years after 1950) into the given formula: 
11eb0d3b_975c_e0b7_9790_af498b8aeec4_TB1243_11 = 9.8*cos(pi/6*(20-1))+20 
≈ 30.9% 
Therefore, the formula gives an approximation of 30.9%, which is closest to the actual tax load of 31.4% in 1970. So the best choice is C.

The Approximate Percent of Average Income Used to Pay