Multiplying any Number with 99, 999, 9999 etc using Speed Mathematics
Example 1

Calculate 24 * 99

Solution

1. Decrement one from the number. So here 24-1 = 23

2. Decrement each digit of the number obtained from 9. Here we got 23. Now 9-2 = 7 and 9-3=6. So we have 76

3. Just write these numbers together. That is we have 23 and 76. Hence answer is 2376

Example 2

calculate 2358 * 9999

Solution

1. Decrement one from the number. So here 2358-1 = 2357

2. Decrement each digit of the number obtained from 9. Here we got 2357. Now 9-2 = 7 , 9-3=6 , 9-5=4 and 9-7=2. So we have 7642

3. Just write these numbers together. That is we have 2357 and 7642. Hence answer is 23577642

Example 3

calculate 758 * 99999

Solution

1. Since the number of digits in 99999 is 5, we need to write 758 as 00758 in order to treat it as a 5 digit number

1. Decrement one from the number. So here 00758-1 = 00757

2. Decrement each digit of the number obtained from 9. Here we got 00757. Now 9-0=9, 9-0=9, 9-7=2, 9-5=4, 9-7=2. So we have 99242

3. Just write these numbers together. That is we have 00757 and 99242. Hence answer is 0075799242 or 75799242

 
 
 
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showing 11-20 of 21 comments,   sorted newest to the oldest
SANJAY PAUL
2015-09-15 12:13:34 
Just fun
23458*999

Just subtract last 3 digit
1000 - 458 =  542
Write at right : 542

Then add 1 to first 2 digit : 23+1=24

subtract from original 5 digit : 23458-24 = 23434

So answer is 23434542
(0) (0) Reply
Nadalchukwu
2014-03-06 23:57:56 
23458*999
23458(1000-1)
23458*1000 - 23458*1
23458000-23458
=23434542

786*99= 786(100-1)
=786*100 - 786*1
=78600-786
=77814
(0) (0) Reply
kajal
2013-08-22 15:20:55 
what if number is below 9  like 65424355*7
(0) (0) Reply
Padmanaban
2013-08-07 13:40:54 
SOLVE

24135*99
(0) (0) Reply
sam
2013-10-23 17:59:39 
=24135(100-1)
=24135(100)-24135(1)
=24135*100-24135
=2413500-24135
=2389365
(0) (0) Reply
Gaurav
2013-08-23 19:40:01 
its possible to do so
24135-1 ==   24134

now   24134  99
       -    241  34

      =  23893 65
(0) (0) Reply
Priya
2013-08-09 17:04:16 
Since the number of '9' are less than the number of digits in 24135, this method may not be applicable for  24135 * 99
(0) (0) Reply
Vanga Kishore
2013-07-12 07:43:59 
take 6345
according to above process 
6345-1=6344
we have only two digit number 99 put two zeroes before 99 i.e 0099
according to above process
0-6,0-3,9-4,9-4
therefore coming values are -6,-3 and 5,5 from those only two negative values -6 and -3 substract last two digits  of 6344     separately from

        634 4(take barrow from 3 at that place remaining one is  2)
i.e       -6-3 55
            | |
        62 8 1 55 this is correct answer
(0) (0) Reply
jiju
2013-02-21 11:17:57 
@anonymous

One way to solve this is given below

6345 * 99 = 6345(100 - 1) = 634500 - 6345 = 628155 This method is applicable for all the problems
(0) (0) Reply
kishore
2013-07-12 07:20:38 
ok it is correct   2358*9999=2358(10000-1)=23580000-2358
just compare to that one it should be lenth and time taking when we subtract 2358 from that value ......23580000
(0) (0) Reply
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