Mentally Find 10 More or 10 Less

Students will mentally determine what is 10 more or 10 less than a given two-digit number without counting by ones. Students use understanding of place value to see that only the tens digit changes when adding or subtracting 10.

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Grade 1 · Comparing and Computing with Two-Digit Numbers · question 1 of 3

0 of 12

12 rungs. A star at the top.

= 13 + 10

How it is taught

0:00 of 2:22

10 less is one ten smaller.

The ones digit stays put.

Read it: 10 more, 10 less: 1 jump

Start at 64. 1 jump of 10 forward lands on 74. 1 jump of 10 back lands on 54.

Find your number on the line.
Jump forward 10 for 10 more, or back 10 for 10 less.
Read the number you land on.

Each jump of 10 moves 1 mark along the line.

The tens change and the ones stay: 54, 64, 74.

You do not count 10 little steps. 1 jump is 10.

10 more: jump forward 10. 10 less: jump back 10.

Counting 1 more from 64 instead of 10 more.

A jump is 10, not 1. From 64, 10 more is 74 and 10 less is 54.

12 − 10 = ___ — 2. 1 jump back of 10 from 12 lands on 2 — 1 mark along, not 10 little steps.

10 more & 10 less than 47

What is ten more than forty-seven? What is ten less? Let's find out without counting one by one.

Forty-seven has four tens and seven ones.

Here is forty-seven on the number line, between forty and fifty.

Ten more means we hop up by ten — landing on fifty-seven.

Look! The tens went from four to five. The ones stayed at seven.

Ten less means we hop back by ten — landing on thirty-seven.

Grade 1 · Place value tells us — only the tens digit changes

The tens went from four to three. The ones is still seven.

Ten more or ten less only changes the tens digit. The ones digit stays the same!

What you see

While they climb, your page writes one true line to ask about tonight, and a short note each Sunday.

MayaGrade 3 · Mathematics

Did you know?

A chessboard has 64 squares — share them out between the 8 rows and each row holds exactly 8.

Today’s goal: 1 star — one skill mastered, every rung of its ladder climbed
Climbing now: Divide within 100

An example student.

MayaGrade 3 · Mathematics

Maya earned 2 stars this week — Interpret multiplication as equal groups, which took 6 answers over 3 days before its star landed 3 days ago and Multiply by 6, 7, 8 and 9. Next up: Divide within 100.

An example week.

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