Perfect1600

Digital SAT · Solve it in Desmos

How to Solve Percentages on Desmos (Digital SAT)

With the relationship set up, the calculator handles the arithmetic and keeps a grid-in clean. Translating the words and choosing the right base are the parts you own.

Perfect1600 Content Team·Uses the same Desmos calculator that is built into the Digital SAT

Full method for percentages

The Desmos steps

  1. 1

    Type the relationship

    Enter it directly, like 15/60 for "15 is what percent of 60", and read the decimal.

  2. 2

    Chain the factors

    For stacked changes, type the base times each factor, like 120 * 0.75 * 1.08.

  3. 3

    Convert to a percent

    Multiply a decimal by 100, and confirm you reported what was asked.

Open a real question in the same Desmos calculator you get on Perfect1600, with the setup already typed in:

Worked in Desmos

Easy example
1515 is what percent of 6060?
A
4%4\%
25%25\%
C
45%45\%
D
75%75\%

A: Incorrect. 4%4\% divides 6060 by 1515; the part goes over the whole.

B: Correct. 1560=0.25=25%\frac{15}{60}=0.25=25\%.

C: Incorrect. 45%45\% uses the difference 60−1560-15.

D: Incorrect. 75%75\% is the complementary part, not 1515 of 6060.

Explanation

15/60 = 0.25 = 25%.

Medium example
The number of members of a club decreased from 500 to 460. What was the percent decrease in the number of members?
88
B
9.29.2
C
4040
D
9292

A: Correct. The decrease is 500−460500=40500=0.08=8%\frac{500 - 460}{500} = \frac{40}{500} = 0.08 = 8\%.

B: Incorrect. This divides the change by 460 instead of 500.

C: Incorrect. This gives the raw change, 40, not the percent.

D: Incorrect. This computes 460500\frac{460}{500}, the remaining percent.

Explanation

40500=8%\frac{40}{500} = 8\%.

Hard example
A jacket priced at 120 dollars is discounted by 25%, and then a 8% sales tax is applied to the discounted price. What is the final price, in dollars?
A
90.0090.00
97.2097.20
C
99.6099.60
D
129.60129.60

A: Incorrect. This applies the discount but omits the sales tax.

B: Correct. 120×0.75×1.08=97.20120 \times 0.75 \times 1.08 = 97.20 dollars.

C: Incorrect. This combines the percents into a single 17% reduction.

D: Incorrect. This applies the 8% tax but omits the discount.

Explanation

120×0.75×1.08=97.20120 \times 0.75 \times 1.08 = 97.20.

Detailed explanation

The 25% discount multiplies by 0.75 to give 90, and the 8% tax multiplies by 1.08 to give 90×1.08=97.2090 \times 1.08 = 97.20. Forgetting the tax gives 90, and forgetting the discount gives 129.60.

Try it with the calculator

Question 1easy

What is 10% of 470?

Question 2easy

A container holds 320 marbles. Of these marbles, 10% are red. How many of the marbles are red?

Question 3 is ready when you are

Keep going with more questions of this type, each with the same step-by-step reasoning. Free to start.

Start the free diagnostic

Desmos questions

Can Desmos solve percentages questions on the SAT?

With the relationship set up, the calculator handles the arithmetic and keeps a grid-in clean. Translating the words and choosing the right base are the parts you own.

Is the Desmos calculator really built into the Digital SAT?

Yes. The Bluebook testing app includes the Desmos graphing calculator on every Math question, so the method here is one you can use on test day, not a workaround.

Should I still learn the algebra?

Yes. Desmos is fastest when you know what to type and what to read. Learn the underlying method on the full guide, then use the calculator to move quickly and to check your work.

Master percentages, calculator and all

Every Digital SAT question type comes with the method, the Desmos shortcut, and free practice with instant feedback.

See the full methodTake the free diagnostic