Question

Cait purchases a $20 item at a store. She uses a coupon to receive a 15% discount and she pays 6% on the item. She calculates the total cost, in dollars, of the item using the expression shown.
Cait's expression: (1.15)(1.06)(20)

Part A: Describe the error in the expression Cait used for her calculation.

Part B: Show or explain how you would calculate the total cost of Cait's purchase.

Answer 1

A) Cait made two errors:

1. a discount is a deduction so it should be subtracted from the 100% (1.00 - 0.15 = 0.85), not added to 100% (1.00 + 0.15 = 1.15).
2. she paid 6% of the discounted amount, not 6% in addition to the discounted amount.

B) Original amount × Percent remaining after discount × percent paid

= (20)(0.85)(0.06)

= $1.02