Aptitude - Number
6.
Find the unit digit in the product (658 x 539 x 476 x 312) :
Answer
Product of unit digits = 8 x 9 x 6 x 2 = 864
∴ Required unit digit = 4.
Answer :
Option BExplanation :
Product of unit digits = 8 x 9 x 6 x 2 = 864
∴ Required unit digit = 4.
7.
Which one of the following will divide (461 + 462 + 463 + 464) completely ?
Answer
(461 + 462 + 463 + 464)= 460 x (4 + 42 + 43 + 44)
= 460 x 340, which is divisible by 10.
Answer :
Option BExplanation :
(461 + 462 + 463 + 464)= 460 x (4 + 42 + 43 + 44)
= 460 x 340, which is divisible by 10.
8.
Which of the following numbers is prime ?
Answer
√437 < 21
Prime numbers less than 21 are 2, 3, 5, 7, 11, 13, 17, 19
Now test the divisiblity of each given numbers by each of these nmubers.
161 is divisible by 7, 221 is divisible by 13 and 437 by 19.
373 is not divisible by any of these numbers.
∴ 373 is a prime number.
Answer :
Option CExplanation :
√437 < 21
Prime numbers less than 21 are 2, 3, 5, 7, 11, 13, 17, 19
Now test the divisiblity of each given numbers by each of these nmubers.
161 is divisible by 7, 221 is divisible by 13 and 437 by 19.
373 is not divisible by any of these numbers.
∴ 373 is a prime number.
9.
517?324 is exactly divisible by 3, the smallest digit in place of ? is :
Answer
Sum of all the digits of the number = 5 + 1 + 7 + ? + 3 + 2 + 4
= (22 + ?), must be divisible by 3
∴ ? = 2
Answer :
Option CExplanation :
Sum of all the digits of the number = 5 + 1 + 7 + ? + 3 + 2 + 4
= (22 + ?), must be divisible by 3
∴ ? = 2
10.
What least number must be added to 1056 to get a number exactly divisible by 23 ?
Answer
On dividing 1056 by 23, remainder is 21.
∴ Number to be added is = 23 − 21 = 2
Answer :
Option AExplanation :
On dividing 1056 by 23, remainder is 21.
∴ Number to be added is = 23 − 21 = 2
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