Estimate to Check

Round first, and spot an answer that can't be right.

Warm-up, learn, try it together, practice, then a quick check. About 15 minutes.

What children learn in Level 15

Before you trust an answer, check that it's about the right size. Round each number to its greatest place. 243 is about 200, and 36 is about 40.
So 243 times 36 should be near 8,000. Our answer, 8,748, is close, so it makes sense.
Now say someone gets 87,480. The estimate shows that's about ten times too big. A place must have slipped.
An estimate won't give the exact answer, but it catches big mistakes fast. Use one every time you multiply.

Georgia's K-12 Mathematics Standards:

5.NR.2.1 — Fluently multiply multi-digit (up to 3-digit by 2-digit) whole numbers to solve authentic problems.