Estimation and order of magnitude

Sometimes the answer choices are far enough apart that a rough calculation is enough. Rounding each number to something friendly and asking roughly how big the answer should be is faster than exact arithmetic and it catches mistakes that exact arithmetic hides.

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LearnWhat it is, how to spot it, a worked example, and where it goes wrong.
Practice — 3-point ladder2 problems. Three in a row finishes it.0/3 in a row · 0/2 solved
Practice — 4-point ladderNo problems written at this tier yet.Nothing written at this tier yet
Practice — 5-point ladderNo problems written at this tier yet.Nothing written at this tier yet
Skill quizFinish every ladder that has problems first.Finish the ladders above first

Before and after

Needs first

NUM-01Place value and digit positions

Opens up

CFT-05Eliminate impossible choices by bounding CFT-06Estimate to the nearest choice

In official papers

No indexed official paper question has been tagged with NUM-12 yet. The index grows one paper at a time, and it records only question numbers, point values and our own skill tags — never the problems themselves.

See the papers indexed so far

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