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Shirt Sale


Alignments to Content Standards: 6.RP.A.3.c

Task


Selina bought a shirt on sale that was 20% less than the original price. The original price was \$ 5 more than the sale price. What was the original price? Explain or show work.

IM Commentary

There are several different ways to reason through this problem; two approaches are shown.

Solutions

Solution: Tape diagram

Solution: A tape diagram (known in some circles as a strip or bar diagram) shows the solution in a very succinct way:

Bar_diagram_a9698d2c8e521e04acb9340dd52a57f8


Since the difference between the original price and the sale price is \$ 5, which is also 20% of the original price, the original price is 5 times \$ 5.

The original price was \$ 25.

Solution: Dividing by a fraction

We know that 20% of the original price is \$ 5. Furthermore, 20% of the original price is the same thing as \frac{20}{100}=\frac15 of the original price. We know that \frac15 of a quantity is 5, so we can solve this problem by dividing 5 by \frac15 (this is a Group Size Unknown problem).

5 \div \frac15 = 25

So the original price was \$ 25.