Can you explain a faster way to do this problem rather than figuring out the grams of protein per dollar for each one? Thank you!

The graph above shows the amount of protein
supplied by five different food products, A, B, C, D,
and E, as a percentage of their total weights. The
costs of 10 grams of products A, B, C, D, and E are
$2.00, $2.20, $2.50, $4.00, and $5.00, respectively.
Which of the five food products supplies the most
protein per dollar? (question 17, Section 4, practice PSAT)

This question might at first seem to be inviting you to do a bunch of calculations to land on the ratios you need. But look closer: You’re given the price of each product at a constant weight, and you’re given the percent or protein by weight for each product. Therefore, you really just need to plug four simple ratios into your calculator, and pick the biggest one. Divide the values from the graph (representing amounts of protein) by the given prices. (Note that you don’t have to calculate the ratio for D, since it’s not an answer choice.)

A: \dfrac{10}{2}=5

B: \dfrac{15}{2.2}=6.818

C: \dfrac{20}{2.5}=8

E: \dfrac{30}{5}=6

Boom! C is the answer.

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