SAT Calculator Strategies • Lesson 2 of 4

Estimation Methods

Round, get a rough target, and use it to eliminate wrong choices and catch slips.

Estimation is a filter, not the final answer. Round the numbers to something friendly, get an approximate result, and any answer choice far from it is gone. It also catches calculator mistakes: a misplaced decimal jumps out the moment you have a rough target in mind.

Rounding to estimate 18 percent of 412 as about 80Estimate first, then eliminate18% of 412≈20% of 400 = 8004074120740target ≈ 807? too small740? too bigA choice near 74 fits; far-off choices are out.
A rough target turns four choices into one or two.

How to estimate well

  1. Round each number to one easy figure.18% of 412 becomes 20% of 400.
  2. Do the easy version in your head.20% of 400 = 80 — your target.
  3. Compare the choices to the target.Keep what is close (about 74); drop 7 and 740.

On graphs, eyeball the answer before reading it exactly — if the calculator says the intersection is at x = 50 but the lines clearly cross near the origin, you typed something wrong. Estimation is the cheapest error-detector you have.

💡
Percentages: 10% is “move the decimal one place,” and you can build 20%, 5%, 15% from there in your head — no calculator needed.
← Time-Saving Techniques Verification Strategies →