## Picking Numbers with Percents

A local electronics store marks up its items 30% from their wholesale cost. At its annual Spring sale, the store discounts the prices of all items by 20%. The sale price is what percent of the wholesale cost?

A. 90%

B. 100%

C. 104%

D. 110%

E. 117%

## Knowsys Method

**Read the problem carefully.** Make careful note that the price is originally INCREASED by 30%, then it is DECREASED by 20%. Also, notice that the problem asks, "the sales price is what percent OF the wholesale cost," not what percent OFF the wholesale cost. That is an important distinction. For instance, if a shirt is discounted by 30%, then the price is 30% OFF, but 70% OF the original price.

**Identify the bottom line. **sale price = what % of wholesale cost?

**Assess your options. **You can solve the problem by working solely with percents, or you can pick numbers. We recommend the latter method because it is more concrete.

**Attack the problem.** Whenever you are picking a number to use in a percent problem, it is easiest to use 100. So, let's say that the wholesale cost of an item is $100. That cost is marked up 30% to create the regular price at which the item is sold to customers. There are two ways to find that price.

100 + (.3)(100) = 130

100 x 1.3 = 130

The regular price of the item (before the sale) is $130. At the sale, this price of $130 is marked down by 20%. There are two ways to find the sale price.

130 - (.2) (130) = 104

130 x .8 = 104

The sale price is $104, and the wholesale cost was $100. 104 is 104% of 100, so the answer is C.

Note: Look at answer choice D. NEVER fall for this trap: 100 + 30 - 20 = 110. Remember that the price goes up by 30%, then decreases by 20% off the NEW price.

**Loop back. **Verify that you solved for the bottom line.

The correct answer is C.

This is a medium level problem.

**Want some help reviewing the math concepts you need to master? **Try out the Knowsys Pre-Algebra Flashcards, the Knowsys Algebra I Flashcards, and the Knowsys SAT & ACT Math Practice book.

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