Question

kelly has $320 dimes and quarters . the total number of coins she has is 4 less than twice the number of dimes she has . which system of equations can determine d, the number of dimes , and q the number quarters , that kelly has

Answer 1

0.1d + 0.25q = 320

d + q + 4 = 2d ⇒ q + 4 = d (we can replace d in the above equation)

0.1(q + 4) + 0.25q = 320

0.1q + 0.4 + 0.25q = 320

0.35q = 319.6

q = 319.6 / 0.35 = 913.14 ≈ 913

0.25 x 913 = $228.25

0.10 x 917 = $91.70

total $319.95

there is not answer that will result in exactly $320

if Kelly has 914 quarters and 918 dimes = (914 x $0.25) + (918 x 0.10) = $320.30.