Eileen saves dimes and quarters. She has 40 coins which totals $6.55, how many of each coins does she has? (has to be a linear equation)

Question

anonymous · Answer

x+y = 40

texaschic101 · Answer

d + q = 40 -->d = 40 - q
0.10d + 0.25q = 6.55
now sub 40 - q in for d in the 2nd equation..
0.10(40 - q) + 0.25q = 6.55
4.00 - 0.10q + 0.25q = 6.55
4.00 + 0.15q = 6.55
0.15q = 6.55 - 4.00
0.15q = 2.55
q = 2.55/0.15
q = 17
now sub 17 in for q in the 1st equation...
d + q = 40
d + 17 = 40
d = 40 - 17
d = 23
check...
0.10d + 0.25q = 6.55
0.10(23) + 0.25(17) = 6.55
2.30 + 4.25 = 6.55
6.55 = 6.55 (correct)
ANSWER : Ellen has 17 quarters totaling 4.25 and 23 dimes totaling 2.30. Together there are 40 quarters and dimes totaling 6.55.