Problem 1 :
7 x 8
Problem 2 :
16 x 7
Problem 3 :
25 x 12
Problem 4 :
4 x 59
Problem 5 :
71 x 7
Problem 6 :
99 x 9
Problem 7 :
7 x 125
Problem 8 :
150 x 9
Problem 9 :
14 x 250
Problem 10 :
4 x 2.5
Problem 11 :
0.4 x 2.5
Problem 12 :
0.4 x 0.25
Problem 13 :
0.04 x 0.25
Problem 14 :
0.007 x 0.49
Problem 15 :
0.9 x 0.999
Problem 16 :
The cost of a pen is $2.50. Find the cost of 8 pens.
Problem 17 :
The cost of apple is $2 per pund. Find the cost of 12.5 lbs of apple.
Problem 18 :
Is the multiplication of two even numbers is even or odd?Give examples.
Problem 19 :
Is the multiplication of two odd numbers is odd or even? Give examples.
Problem 20 :
Is the multiplication of an odd number and an even number is odd or even? Give examples.
1. Answer :
= 7 x 8
= 56
2. Answer :
= 16 x 7
= (10 + 6) x 7
= 70 + 42
= 112
3. Answer :
= 25 x 12
= 25 x (10 + 2)
= 250 + 50
= 300
4. Answer :
= 4 x 59
= 4 x (60 - 1)
= 240 - 4
= 236
5. Answer :
= 71 x 7
= (70 + 1) x 7
= 490 + 7
= 497
6. Answer :
= 99 x 9
= (100 - 1) x 9
= 900 - 9
= 891
7. Answer :
= 7 x 125
= 7 x (100 + 25)
= 700 + 175
= 875
8. Answer :
= 150 x 9
= (100 + 50) x 9
= 900 + 450
= 1350
9. Answer :
= 14 x 250
= (10 + 4) x 250
= 2500 + 1000
= 3500
10. Answer :
4 x 2.5
Assume the given multiplication as 4 x 25. Then, we have
4 x 25 = 100
In the given two numbers, 2.5 constains decimal point and there is one digit after the decimal point.
So, there must be one digit after the decimal point in the answer of 4 x 25.
4 x 2.5 = 10.0
4 x 2.5 = 10
11. Answer :
0.4 x 2.5
We have decimal point in both of the given numbers and there is one digit after the decimal point in each number.
So, there must be two digits after the decimal point in the answer of 4 x 25.
0.4 x 2.5 = 1.00
0.4 x 2.5 = 1
12. Answer :
0.4 x 0.25
We have decimal point in both of the given numbers and there is one digit after the decimal point in 0.4 and that of two digits in 0.25.
So, there must be three digits after the decimal point in the answer of 4 x 25.
0.4 x 0.25 = 0.100
0.4 x 0.25 = 0.1
13. Answer :
0.04 x 0.25
We have decimal point in both of the given numbers and there are two digits after the decimal point in each number.
So, there must be four digits after the decimal point in the answer of 4 x 25.
0.04 x 0.25 = 0.0100
0.04 x 0.25 = 0.01
14. Answer :
0.007 x 0.49
Assume the given multiplication as 7 x 49. Then, we have
= 7 x 49
= 7 x (50 - 1)
= 350 - 7
= 343
We have decimal point in both of the given numbers and there are three digits after the decimal point in 0.007 and that of two digits in 0.49.
So, there must be five digits after the decimal point in the answer of 0.007 x 0.49.
0.007 x 0.49 = 0.00343
15. Answer :
0.9 x 0.999
Assume the given multiplication as 9 x 999. Then, we have
= 9 x 999
= 9 x (1000 - 1)
= 9000 - 9
= 8991
We have decimal point in both of the given numbers and there is one digit after the decimal point in 0.9 and that of three digits in 0.999.
So, there must be four digits after the decimal point in the answer of 9 x 999.
0.9 x 0.999 = 0.8991
16. Answer :
Cost of 8 pens :
= 8 x cost of 1 pen
= 8 x $2.50
= 2 x 4 x $2.50
= 2 x $10
= $20
17. Answer :
Cost of 12.5 lbs of apple.
The cost of apple is $2 per pund. Find the cost of 12.5 lbs of apple.
= 12.5 x cost of 1 lb of apple
= 12.5 x $2
= (12 + 0.5) x $2
= $24 + $1
= $25
18. Answer :
The multiplication of two evan numbers is always an even number.
Examples :
2 x 4 = 8
6 x 14 = 84
19. Answer :
The multiplication of two odd numbers is always an odd number.
Examples :
7 x 9 = 63
5 x 13 = 65
20. Answer :
The multiplication of an odd number and an even number is always an even number
Examples :
3 x 8 = 24
6 x 15 = 90
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