Question

Luke has 15 coins. He has only nickels and dimes. If the total value of the coins is $1.20, how many nickels does he have ? A. 5 B. 6C. 8 D. 9

Answer 1

We have the following:

we can solve the question by means of the following system of equations

let x, nickel ($0.05)

let y, dime ($0.10)

$\begin{gathered} x+y=15\rightarrow y=15-x \\ 0.05x+0.10y=1.20 \end{gathered}$

solving:

$\begin{gathered} 0.05x+0.10\cdot(15-x)=1.20 \\ 0.05x+1.50-0.1x=1.20 \\ 0.1x-0.05x=1.50-1.20 \\ 0.05x=0.30 \\ x=\frac{0.30}{0.05} \\ x=6 \end{gathered}$

The answer is B. 6 nickels