MULTIPLYING TWO DIGIT NUMBERS BY ONE DIGIT NUMBERS
We can follow the steps given below to multiply a two digit number by a one digit number mentally.
Step 1 :
Break the two digit number into tens and ones.
Example : The two-digit number 23 is close to the round figure 20. So, we can break 23 into (20 + 3). The two-digit number 29 is close to the round figure 30. So, We can break 29 into (30 - 1).
Step 2 :
Multiply tens by the one digit number.
Steps 3 :
Multiply ones by the one digit number.
Step 4 :
Add the results of step 3 and step 4.
Video Lesson
Solved Examples
Evaluate each of the following expressions.
Example 1 :
14 x 5
Solution :
= 14 x 5
= (10 + 4) x 5
= 10 x 5 + 4 x 5
= 50 + 20
= 70
Example 2 :
12 x 9
Solution :
= 12 x 9
= (10 + 2) x 9
= 10 x 9 + 2 x 9
= 90 + 18
= 108
Example 3 :
24 x 6
Solution :
= 24 x 6
= (20 + 4) x 6
= 20 x 6 + 4 x 6
= 120 + 24
= 144
Example 4 :
19 x 6
Solution :
= 19 x 6
= (20 - 1) x 6
= 20 x 6 - 1 x 6
= 120 - 6
= 114
Example 5 :
38 x 5
Solution :
= 38 x 5
= (40 - 2) x 5
= 40 x 5 - 2 x 5
= 200 - 10
= 190
Example 6 :
49 x 7
Solution :
= 49 x 7
= (50 - 1) x 7
= 50 x 7 - 1 x 7
= 350 - 7
= 343
Example 7 :
78 x 4
Solution :
= 78 x 4
= (80 - 2) x 4
= 80 x 4 - 2 x 4
= 320 - 8
= 312
Example 8 :
81 x 6
Solution :
= 81 x 6
= (80 + 1) x 6
= 80 x 6 + 1 x 6
= 480 + 6
= 486
Example 9 :
93 x 7
Solution :
= 93 x 7
= (90 + 3) x 7
= 90 x 7 + 3 x 7
= 630 + 21
= 651
Example 10 :
99 x 9
Solution :
= 99 x 9
= (100 - 1) x 9
= 100 x 9 - 1 x 9
= 900 - 9
= 891
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