Question

(999999999)⁹⁹⁹⁹⁹x 9999999 x (999999999999999999)⁹⁹⁹⁹⁹ = ?​

Answer 1

Step-by-step explanation:

What is 999,999,999,999 x 999,999,999,999=?

Very Easy To Do This without using any mathematical formula if all digits are 9.

There could be two cases:

a) Both the numbers are same in length

b) One number is greater than the other.

Solving a)

Step1) Subtract 1 from the number

Step2) Add exactly the same number os zeros as there are 9 in step 1 and then add 1 in the last

Eg: If you do 9999 x 9999

Step1) 9998 (By Subtracting 1 from the number)

Step 2) Add 0001 to the above string and you get the answer i.e. 99980001

Solving b) When one number is greater than the other in length eg: 9999 x 999

Step1) Take the shorter number for consideration first , So we will consider 999 first.

Step2) Subtract 1 from Step 1 Result, You get 998

Step 3) Now add the extra 9s to Step 2 which are there in the larger number, So in above case there’s only 1 extra 9, So you get 9989

Step 4) Add exactly the same number Zero’s as there are 9 in step 2 and then add 1 in the last So you add 001 to Step 3 and you get the answer as 9989001

Eg: 9999999999 x 99999 (10 Nines x 5 Nines)

Step 1) 99998 (Subtract 1 from smaller numer)

Step 2) 99998 99999 (Add Extra Nines to Step 1)

Step 3) 99998 99999 00001 (Replace (9s with 0 and 8 with 1 in Step 1)

So the final answer is 999989999900001.

So no need to do heavy calcualtions, simple counting works here :)

Hence to answer your questions:

999,999,999,999 x 999,999,999,999=?

You have 12 nines in both numbers

Step 1) Subtract 1 from the number you get 999,999,999,998

Then replace all 9s with 0s and 8 with 1 and you get the final answer when you append it to Step 1, So you append 000,000,000,001 to Step 1 and your final answer becomes 999,999,999,998,000,000,000,001

hope it helps you

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