Plugging In: Invisible Plugging In - Percents
If Martha earns three times as much as Sharon, who earns 25% of Samantha's earning, Sharon's earning constitutes what percent of the total earning of all three?
Incorrect.
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Incorrect.
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Incorrect.
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Correct.
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Start by __Plugging In__ for the smallest invisible variable—in this case, Sharon's earnings. Use a good number, like 2. If Sharon earns $2, then Samantha earns $$4\times 2=\$8$$ and Martha earns $$3\times2=\$6$$.
Their total earnings are $$2+6+8=\$16$$. Therefore, Sharon's earnings equal $$\frac{2}{16} = \frac{1}{8}$$, or 12.5%, of the lot.
__Alternative explanation__:
Since the problem uses percents and not real numbers, __Plug In__ 100. Make the $100 the number you're taking the percent from. In this case, Sharon's earnings are 25% of Samantha's earnings. Assume that Samantha earns $100 so that Sharon earns $25 and Martha earns $$3\cdot 25 = \$75$$.
Using these numbers, Sharon earns $25 out of a total of $$100+25+75 = \$200$$. Translate this fraction into percents by multiplying by 100:
>$$\displaystyle \require{cancel}\require{enclose} \frac{25}{200} = \frac{25}{200} \times 100\% = \frac{25}{2}\% = 12.5\%$$.
Incorrect.
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10%
12.5%
15%
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25%
