10 or 100 more or less: what children learn
In the game, children balance the scales, such as 456 + 100 = ? or 456 + ? = 556. In the Quick quiz most questions are straightforward, such as 100 more than 456 = 556. The interesting ones cross a boundary: 10 more than 395 is 405, because the tens digit goes from 9 to 0 and the hundreds go up by one. The game deliberately includes many of these, and the wrong answers include the most common slips, such as changing the wrong digit.
Supports part of Common Core 2.NBT.B.8. This focused game does not cover the entire standard.
Common Core connection: 2.NBT.B.8. This is focused practice for part of the standard.
How to play
Make both sides of the scales equal. Tap the weight that fills the gap, or press 1 to 4. Each game has 8 questions and no timer. If a weight doesn't balance, the scales tip towards the heavier side and you get one more try. You get a point for each one balanced first time. For a quicker go, choose Quick quiz: 10 multiple-choice questions in 120 seconds (choose Relaxed for more time).
Step by step
- Decide which digit changes. 10 more or less changes the tens. 100 more or less changes the hundreds. The ones never change.
- Change that digit by one. 10 more than 263: the tens digit 6 becomes 7, giving 273.
- Watch for crossing a hundred. 10 more than 395: the tens digit 9 cannot become 10, so it becomes 0 and the hundreds go up by one. The answer is 405.
- Check by counting on. Count in tens from the number: 395, 405. If that sounds odd, count 395, 400, 405.
Worked examples
Example 1: What is 100 less than 718?
Working: The hundreds digit 7 becomes 6.
Answer: 618
Example 2: What is 10 less than 304?
Working: There are 0 tens, so we take one hundred and make it ten tens: 304 − 10 = 294.
Answer: 294
Example 3: What is 10 more than 992?
Working: The tens go from 9 to 0 and the hundreds from 9 to 10, giving 1,002. (The game keeps answers below 1,000, but this is a good challenge.)
Answer: 1,002
Common mistakes and how to fix them
- Changing the hundreds when asked for 10 more. Say the question aloud and point to the tens digit before answering.
- Writing 10 more than 395 as 3,105. Use place value counters: ten tens make one hundred, so exchange them.
- Getting 10 less than 304 wrong because there are no tens. Count back in tens: 304, 294. Or think of 304 as 29 tens and 4 ones.
Activities to try at home
- Use money: how much is 10¢ more than $3.95?
- Play 'up and down the stairs': each step is 10 more; each floor is 100 more.
- Ask for 10 or 100 more than door numbers, page numbers or scores.
Ideas for the classroom
- Use a 1 to 1,000 grid or a number line marked in tens.
- Play a chain game: each student adds 10 or 100 and passes it on.
- Use place value counters on a chart to show exchanging ten tens for a hundred.
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
How should I choose this game for my learner?
Supports part of Common Core 2.NBT.B.8. This focused game does not cover the entire standard.
Why are there so many questions like 10 more than 395?
Because crossing a hundred is where mistakes happen, so it gives the most useful practice.
What is the US equivalent?
The closest Common Core standard is 2.NBT.B.8 (Grade 2): mentally add or subtract 10 or 100 to or from a number between 100 and 900.