Trick 5: Multiplication with 25, 125, 625.
Concept :
25 = 100/ 4
125 = 1000/8
625 = 10000/16
example 1:
64 × 25 = ?
Sol. :
64 × 25
= 64 × (100 / 4)
= 16 × 100
= 1600
Answer is : 1600
example 2:
192 × 125 = ?
Sol. :
192 × 125
= 192 × (1000 / 8)
= 24 × 1000
= 24000
Answer is : 24000
example 3:
272 × 625 = ?
Sol. :
272 × 625
= 272 × (10000 / 16)
= 17 × 10000
= 170000
Answer is : 170000
Trick 6: Multiplication with 15.
Concept :
15 = 15 × (10 / 10)
= (3 / 2) × 10
= (1 + 1/2) × 10
[ Answer = (Number + (1/2) number) × 10 ]
example 1:
526 × 15 = ?
Sol. :
= (526 + (1/2) × 526) × 10
= (526 +263) × 10
= 789 × 10
= 7890
Answer is : 7890
example 2:
223 × 15 = ?
Sol. :
= (223 + (1/2) × 223) × 10
= (223 +111.5) × 10
= 334.5 × 10
= 3345
Answer is : 3345
Trick 7: Multiplication with 11.
Concept : Start from the right digit , add to next digit to the left in following manner. and add carry if it is.
example 1:
3524 × 11 = ?
Sol. :
example 2:
517328 × 11 = ?
Sol. :
Trick 8: When unit digit is 5 and the difference of the number is 10.
example 1:
75 × 65 = ?
Sol. :
= 6 × (7+1) / 75
= 6 × 8 / 75
= 48 / 75
Answer is : 4875
example 2:
105 × 95 = ?
Sol. :
= 9 × (10+1) / 75
= 9 × 11 / 75
= 99 / 75
Answer is : 9975
Practice Questions :
Concept :
25 = 100/ 4
125 = 1000/8
625 = 10000/16
example 1:
64 × 25 = ?
Sol. :
64 × 25
= 64 × (100 / 4)
= 16 × 100
= 1600
Answer is : 1600
example 2:
192 × 125 = ?
Sol. :
192 × 125
= 192 × (1000 / 8)
= 24 × 1000
= 24000
Answer is : 24000
example 3:
272 × 625 = ?
Sol. :
272 × 625
= 272 × (10000 / 16)
= 17 × 10000
= 170000
Answer is : 170000
Trick 6: Multiplication with 15.
Concept :
15 = 15 × (10 / 10)
= (3 / 2) × 10
= (1 + 1/2) × 10
[ Answer = (Number + (1/2) number) × 10 ]
example 1:
526 × 15 = ?
Sol. :
= (526 + (1/2) × 526) × 10
= (526 +263) × 10
= 789 × 10
= 7890
Answer is : 7890
example 2:
223 × 15 = ?
Sol. :
= (223 + (1/2) × 223) × 10
= (223 +111.5) × 10
= 334.5 × 10
= 3345
Answer is : 3345
Trick 7: Multiplication with 11.
Concept : Start from the right digit , add to next digit to the left in following manner. and add carry if it is.
example 1:
3524 × 11 = ?
Sol. :
Answer is : 38764
example 2:
517328 × 11 = ?
Sol. :
Answer is : 569118
example 1:
75 × 65 = ?
Sol. :
= 6 × (7+1) / 75
= 6 × 8 / 75
= 48 / 75
Answer is : 4875
example 2:
105 × 95 = ?
Sol. :
= 9 × (10+1) / 75
= 9 × 11 / 75
= 99 / 75
Answer is : 9975
Practice Questions :
1. 53 × 86 = ?
2. 95 × 89 = ?
3. 109 × 112 = ?
4. 88 × 104 = ?
5. 57368
× 11 = ?
6. 85 × 75 = ?
7. 63 × 67 = ?
8. 76 × 36 = ?
9. 16192
× 625 = ?
10. 727 × 15 = ?
11.
534 × 323 = ?
12. 1111 × 111 = ?
13.
685 × 58 = ? [Hint : (685 × 058) ; use
trick 1(ii) ]
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