Trick of the Day - Multiplication by 25, 50, 75, 125

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Trick of the Day - Multiplication by 25, 50, 75, 125

Post by Ani on Mon Feb 23, 2009 3:18 pm

So...
The inaugral trick shall be the simple, basic, yet useful, multiplication by 25 trick

Sooooooooo....
Lets begin

ex.1 - 15 * 25 = ?
1. First, divide the non- 25 number by 4.
2. Write the quotient down (3 in this case since 15/4 = 3R3)
3. Then, if the remainder is:
0 - write down 00 next to the quotient
1 - write down 25 next to the quotient
2 - write down 50 next to the quotient
3 - write down 75 next to the quotient
4. Since the remainder is 3 in our case, write down 75 next to the quotient and... you have your answer

15*25 = 375

Lets look at another one:

ex.2 - 63 * 25 = ?
1. First, divide the non- 25 number by 4.
2. Write the quotient down (15 in this case since 63/4 = 15R3)
3. Then, if the remainder is:
0 - write down 00 next to the quotient
1 - write down 25 next to the quotient
2 - write down 50 next to the quotient
3 - write down 75 next to the quotient
4. Since the remainder is 3 in our case, write down 75 next to the quotient and... you have your answer
63 * 25 = 1575
YEAHHHHHHH!!!!!!!

Now, lets look at multiplication by 50:

ex.1 - 33 * 50 = ?
1. First, divide the non - 50 number by 2.
2. Write the quotient down (16 in this case since 33/2 = 16R1)
3. Then, if the remainder is:
1 - write down 50 next to the quotient
0 - write down 00 next to the quotient
4. Since the remainder is 1 in our case, write down 50 next to the quotient and... you have your answer
33 * 50 = 1650
awesome!!!!!!!!!!!!!!

Now, lets look at multiplication by 75:

ex.1 - 33 * 75 = ?
1. First, multily the non - 75 number by 3, remember the number.
2. Divide the number by 4 Write the quotient down (24 in this case since 99/4 = 24R3)
3. Then, if the remainder is:
0 - write down 00 next to the quotient
1 - write down 25 next to the quotient
2 - write down 50 next to the quotient
3 - write down 75 next to the quotient
4. Since the remainder is 3 in our case, write down 75 next to the quotient and... you have your answer
33 * 75 = 2475
awesome!!!!!!!!!!!!!!

Now, lets look at multiplication by 125:

ex.1 - 33 * 125 = ?
1. First, multily the non - 125 number by 5, remember the number.
2. Divide the number by 4 Write the quotient down (41 in this case since 165/4 = 41R1)
3. Then, if the remainder is:
0 - write down 00 next to the quotient
1 - write down 25 next to the quotient
2 - write down 50 next to the quotient
3 - write down 75 next to the quotient
4. Since the remainder is 1 in our case, write down 25 next to the quotient and... you have your answer
33 * 125 = 4125
Inconcievable!!!!!!!!!!!!!!

PRACTICE PROBLEMS

1. 15*25
2. 33*25
3. 127*50
4. 330*75
5. 15*125
6. 64*75
7. 10*25
8. 65*50
9. 125*125
10. 65*125
11. 75*12
12. 11*125
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Ani
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