Number System
- Which of the following numbers is prime ?
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119 is divisible by 7, 187 is divisible by 11,247 is divisible by 13 and 551 is divisible by 19. So none of the given numbers is prime.
Correct Option: D
119 is divisible by 7, 187 is divisible by 11,247 is divisible by 13 and 551 is divisible by 19. So none of the given numbers is prime.
- The number (10n-1) is divisible by 11 for ?
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For even values of n, the number (10n - 1 ) consists of even numbers of nines and hence it will be divisible by 11.
Correct Option: C
For even values of n, the number (10n - 1 ) consists of even numbers of nines and hence it will be divisible by 11.
- What least number must be added to 1056 get a number exactly divisible by 23 ?
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On dividing 1056 by 23, we get 21 as remainder
∴ Required number to be added = (23 - 21 ) = 2.Correct Option: D
On dividing 1056 by 23, we get 21 as remainder
∴ Required number to be added = (23 - 21 ) = 2.
- If in a long division sum,the dividend is 380606 and the successive remainders from the first to the last are 434, 125 and 413, then the divisor is ?
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Let d = divisor and q = quotient
First remove the last remainder:
d x q + 413 = 380606
d x q = 380193Correct Option: B
Let d = divisor and q = quotient
First remove the last remainder:
d x q + 413 = 380606
d x q = 380193
So d cannot be even (choice d) or a multiple of 5 (choice c).
If we try choice a or b,
a quick division (by calculator) shows that
380193 = 451 x 843, the other two choices.
(In the absence of choices, we could find the prime factors of 380193,
which are 3 x 11 x 41 x 281 and get various candidate divisors from that.)
So one of them is the divisor and the other the quotient.
So we can just check the first remainder:
843 x 4 = 3372
3806 - 3372 = 434 ... a match!
And just to be sure:
451 x 8 = 3608
3806 - 3608 = 198
So the divisor is 843.
- What least value must be given to * so that the number 6135 * 2 is exactly divisible by 9 ?
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6 + 1 + 3 + 5 + x + 2 = 17 + x must be divisible by 9.
So, x =1.Correct Option: B
6 + 1 + 3 + 5 + x + 2 = 17 + x must be divisible by 9.
So, x =1.