Question

You have a piggy bank a total of 72 coins in dime and quarters . If the piggy bank contains 10.80 how many dime are in the piggy bank

Answer 1

$\text{Make a system of equations:}\\\\72=d+q\\\\10.80=0.10d+0.25q\\\\\text{Solve for d:}\\\\-0.25(72=d+q)\\\\10.80=0.10d+0.25q\\\\-18=-0.25d-0.25q\\\\10.80=0.10d+0.25q\\\\-7.20=-0.15d\\\\\text{Divide by -0.15}\\\\48=d\\\\\boxed{\text{48 dimes}}$