SAT Math formula sheet · all 24 · Problem-Solving and Data Analysis · #14 of 24

Percent change on the SAT: How It Is Tested

Percentages

Percent Change diagram for the SAT: Use this equation in 3 different ways: to find the final amount, the original amount, or the percent. Make whatever the
What it is really testingUse this equation in 3 different ways: to find the final amount, the original amount, or the percent. Make whatever the question asks for the unknown, x, plug in numbers for the other two, and let Desmos solve it for you. Very useful and versatile.

The question from the sheet

Medium
SAT Problem-Solving and Data Analysisanswer A
A number nn is increased by 55%. If the result is 378378, what is the value of nn?
✓360360
B252252
C359359
D397397

How the diagram applies

  1. This is the "find the original value" case: final == original ×(1+r)\times (1 + r).
  2. 378=n(1.05)378 = n(1.05), so n=3781.05=360n = \dfrac{378}{1.05} = 360.
  3. The trap is choice C: taking 5%5\% off 378378 gives 359.1359.1, which is not the original.

Answer: A

That is 1 of 24.

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All 24 diagrams

Common Questions

It comes up as an SAT percentages question. Use this equation in 3 different ways: to find the final amount, the original amount, or the percent. Make whatever the question asks for the unknown, x, plug in numbers for the other two, and let Desmos solve it for you. Very useful and versatile.

This is the "find the original value" case: final = original × (1 + r). 378 = n(1.05), so n = 3781.05 = 360. The trap is choice C: taking 5\% off 378 gives 359.1, which is not the original.

No. The SAT reference sheet is twelve geometry formulas and three notes, and Percent Change is not one of them. It is one of the 24 things the test expects you to know without being given them. See what the reference sheet does cover at /blog/sat-math-reference-sheet.