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A Peakscor full-length test in progress: Reading and Writing, Test A, Module 1 of 4, question 7 of 27, with the passage, four answer choices, a highlighter, a 24:18 timer and Flag, Back and Next buttons.

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Every question is tagged by section, domain, skill and difficulty, so you can practice exactly what you need. Full tests run like test day: two Reading & Writing modules, a break, then two Math modules.

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Four modules in official order. The second module of each section adapts to how you did on the first.

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1,023 essential SAT words. Browse the list, flip flashcards, or quiz yourself.

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PEAK Survivor, Hole and Peak Defense: three games powered by SAT practice questions.

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MathProblem-Solving and Data AnalysisHard

A store raises the price of a jacket by 20%. Later, it lowers the new price by 20%. The final price is what percent of the original price?

A80%
B96%Correct
C100%The trap
D104%

Check with $100: $100then$120then$96

  1. Turn each change into a multiplier.

    Up 20% means × 1.20. Down 20% means × 0.80.

  2. Apply them in order.

    1.20 × 0.80 = 0.96

  3. Read the answer.

    The final price is 96% of the original. That’s B.

  4. Why not 100%?

    The 20% cut is taken from the higher price, so it removes more than the 20% increase added.

Test day

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Every Peakscor full test follows this order. In the standard tests, the second module of each section adapts to how you did on the first.

  1. Reading & Writing · Module 1

    27 questions32 min

  2. Reading & Writing · Module 2

    27 questions32 min

    Adapts to how you did on Module 1.

  3. Break

    10 min

  4. Math · Module 1

    22 questions35 min

  5. Math · Module 2

    22 questions35 min

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98 questions · 2 hr 14 min of testing, plus the break

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The Daily, plus 36 practice questions every day: 12 easy, 12 medium and 12 hard, each with a full explanation. Full-length Test A, Challenge Test 1 and all 1,023 vocabulary words are free too. No card needed.

Unlimited practice with no daily limit, plus every full-length test and Challenge test. Pro is $20 a month or $180 a year. Checkout isn’t open yet, so nothing can be bought today.

98 questions across four modules, in the digital SAT’s order: Reading & Writing Module 1 and Module 2 (27 questions each), a 10-minute break, then Math Module 1 and Module 2 (22 questions each). On official timing that’s 2 hr 14 min of testing. You get estimated section scores and a total at the end.

Yes. In the standard full-length tests, Module 2 of each section is the harder version if you get 60% or more of Module 1 right, and the easier version if you don’t. Challenge tests use the hardest material throughout.

Official timing, extended 1.5× time, or untimed, on every test, including the free ones. Extended time allows 48 minutes for each Reading & Writing module and about 52 for each Math module. Untimed removes the clock so you can focus on accuracy.

A quick run with three hearts. Each right answer builds your streak: the questions get harder as it grows, and your points multiply (×2 from three in a row, ×3 from six). A miss costs a heart and drops you back to easy. Best is your longest streak.

Every day at midnight. You get a fresh 12 easy, 12 medium and 12 hard.

No. Peakscor is an independent SAT practice tool, not affiliated with the College Board. Scores shown are estimates.

Your next point starts today.

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Linear functions · Lesson 0

Slope and intercept in context

A linear function can be written f(x)=mx+bf(x) = mx + b. The input is xx, the output is f(x)f(x), and two numbers describe the whole function: the slope mm and the yy-intercept bb.

The slope is a rate. Each time the input goes up by 1, the output changes by mm. In a context, that means mm units of output per 1 unit of input: dollars per month, gallons per mile, degrees per minute. If the input goes up by 10, the output changes by 10m10m.

The intercept is a starting value. When the input is 0, f(0)=m⋅0+b=bf(0) = m \cdot 0 + b = b. In a context, bb is the amount at the start: a sign-up fee, a starting height, the water in a tank before draining begins.

Example: a plan costs f(n)=15n+40f(n) = 15n + 40 dollars after nn months. The 15 multiplies nn, so it is the cost per month: 15 dollars each month. The 40 stands alone, so it is the cost at n=0n = 0: a one-time 40 dollar charge when the plan starts. After 6 months the plan has cost 15(6)+40=13015(6) + 40 = 130 dollars.

The sign of the slope gives the direction. If m>0m > 0, the function is increasing: the output rises as the input rises. If m<0m < 0, it is decreasing. In V(t)=1200−150tV(t) = 1200 - 150t, the slope is −150-150, so the value goes down by 150 each time tt goes up by 1. If m=0m = 0, the function is constant.

To interpret any number, ask one question. Does it multiply the input? Then it is a rate per unit. Does it stand alone? Then it is the value when the input is 0.

Worked example Easy

The total cost, in dollars, of a phone plan after nn months is given by the function f(n)=15n+40f(n) = 15n + 40.

What is the best interpretation of 40 in this context?

  1. The amount, in dollars, by which the total cost increases each month
  2. The cost, in dollars, of the plan at the start, before any months have passedAnswer
  3. The total cost, in dollars, of the plan after 1 month
  4. The total cost, in dollars, of the plan after nn months

How to solve it

  1. The 15 multiplies nn, so it is a rate: 15 dollars for each month.
  2. The 40 stands alone. Set n=0n = 0: f(0)=15(0)+40=40f(0) = 15(0) + 40 = 40. So 40 dollars is the cost before any months have passed.
  3. In context, that is a one-time charge when the plan begins: the cost of the plan at the start.

Why each choice is right or wrong

  • A. Incorrect. This treats 40 as the rate. The rate is the number that multiplies nn: the total cost goes up 15 dollars each month.
  • B. Correct. When n=0n = 0, f(0)=15(0)+40=40f(0) = 15(0) + 40 = 40. The 40 doesn't depend on nn, so it is a one-time cost at the start.
  • C. Incorrect. This reads the constant as the value at n=1n = 1. After 1 month the total is f(1)=15(1)+40=55f(1) = 15(1) + 40 = 55 dollars. The constant is the value at n=0n = 0.
  • D. Incorrect. The total cost after nn months is the whole expression 15n+4015n + 40, which is f(n)f(n). The 40 is only the part that doesn't depend on nn.

Worked example Medium

The amount of fuel, in gallons, remaining in a truck's tank after the truck has traveled dd miles is modeled by the function f(d)=36−0.05df(d) = 36 - 0.05d.

According to the model, how many gallons of fuel does the truck use for every 100 miles it travels?

  1. 0.050.05
  2. 2020
  3. 55Answer
  4. 3131

How to solve it

  1. The slope is −0.05-0.05: for each mile, the fuel remaining goes down by 0.05 gallon. So the truck uses 0.05 gallon per mile.
  2. For 100 miles, multiply the rate by 100: 0.05×100=50.05 \times 100 = 5 gallons.
  3. Check with the function: f(0)=36f(0) = 36 and f(100)=36−5=31f(100) = 36 - 5 = 31. The fuel remaining drops from 36 to 31 gallons, a difference of 5.

Why each choice is right or wrong

  • A. Incorrect. 0.05 gallon is the fuel used per mile. The question asks about 100 miles, so multiply by 100.
  • B. Incorrect. This divides 1 by 0.05, which gives miles per gallon: the truck travels 20 miles on each gallon. The question asks for gallons, not miles.
  • C. Correct. The truck uses 0.05 gallon per mile, so over 100 miles it uses 0.05×100=50.05 \times 100 = 5 gallons. The fuel remaining goes from f(0)=36f(0) = 36 to f(100)=31f(100) = 31.
  • D. Incorrect. f(100)=36−0.05(100)=31f(100) = 36 - 0.05(100) = 31 is the fuel remaining after 100 miles, not the fuel used. The fuel used is 36−31=536 - 31 = 5 gallons.

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