Friends in this post we are providing a very cool and interesting shortcut trick to calculate the unit digits. Problems of finding the unit digits are often asked in MBA Entrance Tests such as CAT, GMAT, MAT, CMAT, XAT and also sometimes in Bank Exams like IBPS PO, IBPS CLERK, IBPS RRB, SBI PO Exams.
THE SHORTCUT
We Start multiplying the unit digits of the given numbers. In the process of multiplying, if we get the products in two digits then we drop the digit at ten’s place and keep on multiplying with the unit digit.
Confused? No problem, Just chill ! Just have a look on the following examples and you will get the trick easily.
Example-1: What is the unit digit in the product 284 * 328 * 477 * 613 ?
Solution: Here we go………….
Start multiplying the unit digits (Shown below as bold digits), one by one.
284 * 3 2 8 * 477 * 613
4 * 8 = 32 ( Drop 3 and continue multiplication with 2)
2 * 7 = 14 ( Drop 1 and continue multiplication with 4)
4 * 3 = 12
At the end we get 2 as the unit digit. Hence, 2 is the final answer.
Lets take another example.
Example- 2: What is the digit in the units place of the product 81 * 82 * . . . . . . * 89 ?
Solution: Friend’s this problem is even more simpler then the first problem. We can answer it in a second without any calculation.
The Answer is 0 (Zero).
Lets see how?
In this series we are having an even number 82 and definitely in the series the number 85 will also be there and that is a multiple of 5. Now, whenever we multiply an even number with any multiple of 5, we always get Zero (0) as the product’s unit place.
So in this case when we multiply 2 (of 82) and 5 (of 85) and we get 10 and its unit digit is 0.
Check out our earlier post PIPES AND CISTERNS-SHORTCUTS
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