Question

A piggy bank contains 350 pennies

and nickels worth $11.90. How many
pennies are in the piggy bank?

Answer 1

140 pennies

Explanation:

Information:

• 1 penny (cent) = $0.01
• 1 nickel = $0.05

Define the variables:

• Let x be the number of pennies.
• Let y be the number of nickels.

If the piggy bank contains 350 pennies and nickels:

`\implies x+y=350`

If the piggy bank contains pennies and nickels worth $11.90:

`\implies 0.01x+0.05y=11.90`

Rearrange the first equation to make y the subject:

`\implies y=350-x`

Substitute the expression for y into the second equation and solve for x:

`\implies 0.01x+0.05(350-x)=11.90`

`\implies 0.01x+17.5-0.05x=11.90`

`\implies -0.04x=-5.6`

`\implies x=140`

Therefore, there are 140 pennies in the piggy bank.