Curriculum › Math ›Grade 3

Grade 3 Math · Level 3, Operations & Reasoning

Estimate and Check Reasonableness

How the lesson starts: Estimate and Check Reasonableness

1. Keeper Kiki's bananas

   Hi friend! Keeper Kiki feeds the zoo monkeys. On Monday they ate 187 bananas. On Tuesday they ate 212. About how many is that? Kiki doesn't need exact. A smart guess will do!

2. Round each number

   Round each number to the nearest hundred. 187 has 1 hundred and 8 tens. 8 tens is past halfway, so round up to 200. 212 has 2 hundreds and just 1 ten, so it stays 200.

3. Pick the close one

   Now add the round numbers: 200 + 200 = 400. Which is closest: 200, 400 or 800? 200 is way too small. 800 is way too big. 400 is just right. So 187 + 212 is about 400!