Estimate the answer

Estimate the answer: what children learn

In this game children round three-digit numbers to the nearest hundred and sort additions by their estimate: about 500, 700 or 900. Estimating first helps children spot a wrong answer from a written method.

Supports part of Common Core 3.NBT.A.1: rounding to the nearest 100, used here to estimate sums. This focused game does not cover the entire standard.

Common Core connection: 3.NBT.A.1. This is focused practice for part of the standard.

How to play

Sort the cards into the right groups. Tap a card, then its group. You can also drag a card, or press the number on its group. Each game has 3 rounds with no timer. Every card is checked as soon as you place it: a card in the wrong group comes back with a hint, and you get a point for each card you place right first time. For a quicker go, choose Quick quiz: 10 multiple-choice questions in 150 seconds (choose Relaxed for more time).

Step by step

1. Round each number. Round to the nearest hundred: 322 is about 300, and 230 is about 200.
2. Add the rounded numbers. 300 + 200 = 500.
3. Use the estimate to check. If your written answer is far from 500, check it again.
4. Halfway rule. Numbers ending in 50 or more round up. 250 rounds to 300.

Worked examples

Common mistakes and how to fix them

• Rounding to the nearest ten instead of the nearest hundred. Look at the tens digit to decide whether to round the hundreds up or down.
• Calculating exactly instead of estimating. An estimate should be quick. Round first, then add.
• Always rounding down. Use a number line: is the number nearer 300 or 400?

Activities to try at home

• Estimate the total of a shopping list before adding it up.
• Guess how many steps to the end of the street, then check.
• Estimate the total of two house numbers.

Ideas for the classroom

• Students estimate before every written calculation and tick when the answer is close.
• Show an answer that is clearly wrong and ask students to use estimation to explain why.
• Place numbers on a 0 to 1,000 number line to practice rounding.

Free printable game and worksheet

The free printable starts with a game sheet, such as a color-by-answer picture, an answer maze or a secret-code joke, followed by a worksheet. Both use the same checked questions as the online game, and the answers are on the last page. Print it, or save it as a PDF from your browser’s print menu.

Open the free printable game and worksheet

Frequently asked questions

Related topics

• Column addition and subtraction (Grade 3 math) – Add and subtract 3-digit numbers with the column method, exchanging when you need to. A free Grade 3 math game.
• Rounding to 10, 100 and 1,000 (Grade 4 math) – Round numbers up to 9,999 to the nearest 10, 100 or 1,000. Free Grade 4 math game.
• Hundreds, tens and ones (Grade 2 math) – Quiz race on the value of each digit in a three-digit number. Free Grade 2 math game.
• Addition and subtraction facts to 20 (Grade 2 math) – Type as many addition and subtraction facts to 20 as you can in 60 seconds. Free Grade 2 math game.
• Column methods with 4 digits (Grade 4 math) – Add and subtract 4-digit numbers with the column method. A free Grade 4 math game.
• Missing numbers and inverse operations (Grade 4 math) – Use the inverse to find the missing number in □ + 2,350 = 5,000. A free Grade 4 math game.

Back to Grade 3 math