Melissa used her credit card to buy a $745 refrigerator. She kept the refrigerator for exactly nine years, during which time it consumed an average of $0.19 of electricity every day. Melissa’s credit card has an APR of 16.84%, compounded monthly. Melissa paid off her refrigerator by making identical monthly payments for four years. If she made no other purchases with her card, what percentage of the lifetime cost of the refrigerator did the electricity make up? (Assume that two of the years were leap years, and round all dollar values to the nearest cent.)

Question

nethercreep333 · Answer

PMT = 745(.1684/12) / [1 - (1 + .1684/12)^(-12 * 4)] 

PMT = 21.435386171474506874033032721193 

she paid 
21.44 a month for 4 years 

21.44 * 12 * 4 = 1029.12 total paid on her credit card 

.19(365 * 7 + 366 * 2) 
.19(2555 + 732) 
.19 * 3287 
624.53 in electric 


624.53 / (624.53 + 1029.12) 

624.53 / 1653.65 

0.37766758382971003537628881565023 

37.77%

nethercreep333 · Answer

(medal if this helps)