Question

Jimmy has a pocket full of nickels and quarters. Their are a total of 40 coins. When he added it all up he had $5.20. How many nickels did he have?

Answer 1

Assuming x = nickels, y = quarters

$x + y = 40 \\ 0.05x + 0.25y = 5.20$

$x + y = 40 \\ x = 40 - y$

Substitute that into
$0.05(40 - y) + 0.25y = 5.20 \\ 2 - 0.05y + 0.25y = 5.20 \\ 0.2y = 3.20 \\ y = 16$

Substitute that into
$x + 16 = 40 \\ x = 24$

Answer : He has 24 nickels.

Hope this helps. - M