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Mentally Find 10 Less

Students mentally find 10 less than a given two-digit number by decreasing the tens digit by one while keeping the ones digit the same (e.g., 10 less than 67 is 57).

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Mentally Find 10 Less

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

0 of 12

12 rungs. A star at the top.

24 − 10 =

How it is taught

0:00 of 2:26

10 less is the next smaller ten.

Only the tens place changes.

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.

  1. Find your number on the line.
  2. Jump forward 10 for 10 more, or back 10 for 10 less.
  3. 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.

47 − 10 = ___ — 37. 1 jump back of 10 from 47 lands on 37 — 1 mark along, not 10 little steps.

10 less than 67

Today we'll find 10 less than a number, just in our heads. Let's try 67.

Here is our number — sixty-seven.

The 6 is in the tens place, and the 7 is in the ones place.

10 less means we take away one ten — so we look at the tens digit.

Six tens minus one ten is five tens. The 6 becomes a 5.

The ones digit doesn't change — it stays as 7.

So our new number is fifty-seven.

Let's check on a number line. Here is 67.

Hop back ten, and we land on 57. It works!

10 less than 67?tensones675− 1067 − 10 = 5750705560656757− 10ANSWER5710 less than 67
Grade 1 · Take away one ten, keep the ones

Ten less than 67 is 57. Just lower the tens digit by one and keep the ones 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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