Question

Hakim invests $700 in a bank that pays 5% simple interest annually. After one year he uses the money in his account to buy a computer. The original cost of the computer is $750 The computer is on sale for a 20% discount off of the original cost. The sales tax is 4% of the sale price. After purchasing the computer, how much does Hakim have left in his bank account?

Answer 1

$111

Explanation:

The bank balance is ...

$700 × (1 + 0.05) = $735

The cost of the computer is ...

$750 × (1 -0.20) × (1 +0.04) = $624

The remaining bank balance after paying for the computer is ...

$735 -624 = $111

_____

When you add a percentage, you effectively multiply by the sum of 1 and that percentage. The same is true if the amount "added" is negative (as for a discounted price).

(original amount) + (percentage)×(original amount)

Use the distributive property to factor out the original amount:

= (original amount)×(1 + percentage)