Represent the expression as a math sentence and find the unknown number.

9 tens + 5 ones = ⬜

90+5=95

9 tens + 5 ones = 95

5 tens + ⬜ ones = 58

5 tens is 50. We get the math sentence: 50 +⬜=58

⬜ = 58-50

58-50=8

5 tens + 8 ones = 58

7 tens - 6 ones = ⬜

70-6=64

7 tens - 6 ones = 64

8 tens - ⬜ ones = 73

80-⬜=73

⬜=80-73

80-73=7

8 tens - 7 ones = 73  

Back to practice

In what ways can we write down the numbers? The fastest one is to use numbers. We write down numbers using digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9. When writing a one-digit number, we use only 1 digit.

A two-digit number has two places where we can put a digit. Its place affects the number that it denotes.

We put tens in the first place on the left, and the first digit on the right is for ones. The shapes on the picture are arranged in 3 groups by 10 items in each. These are 3 tens. There are also 6 separate figures, that denote 6 ones. We will put this digit on the right of 3. Thus, we get the number 36.

Sometimes we write the numbers using words in the same way we pronounce them:

Thirty six - 36

Forty eight - 48

Ninety five - 95

Here is one more way to show the number of tens and ones:  

3 tens and 6 ones - 36

4 tens and 8 ones - 48

9 tens and 5 ones - 95 

The skill of representing any expression using numbers is highly significant. To do this, we need to remember the tens and ones place. It will help to add and subtract numbers. Let’s get some practice converting expressions into math sentences and determining their meaning. 

5 tens + 7 ones = ⬜ 

50+7=57, that is why 5 tens + 7 ones = 57. 

90 + ⬜ = 98

What number do we need to add to 90 to get 98? Eight - 8.

That is why 9 tens + 8 ones = 98.

6 tens - one = ⬜ 

60-1=59, that is why 6 tens - one = 59. 

7 tens - ⬜ ones = 61

70 - ⬜ = 61

What number do we need to subtract from 70 to get 61? 9. So, 7 tens - 9 ones = 61.  

Back to practice