Aptitude

If x and y are positive integers such that (3x + 7y) is a multiple of 11, then which of the following will be divisible by 11 ?

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Question:
If x and y are positive integers such that (3x + 7y) is a multiple of 11, then which of the following will be divisible by 11 ?

[A].

4x + 6y

[B].

x + y + 4

[C].

9x + 4y

[D].

4x – 9y

Answer: Option D

Explanation:

By hit and trial, we put x = 5 and y = 1 so that (3x + 7y) = (3 x 5 + 7 x 1) = 22, which is divisible by 11.

(4x + 6y) = ( 4 x 5 + 6 x 1) = 26, which is not divisible by 11;

(x + y + 4 ) = (5 + 1 + 4) = 10, which is not divisible by 11;

(9x + 4y) = (9 x 5 + 4 x 1) = 49, which is not divisible by 11;

(4x – 9y) = (4 x 5 – 9 x 1) = 11, which is divisible by 11.

A 3-digit number 4a3 is added to another 3-digit number 984 to give a 4-digit number 13b7, which is divisible by 11. Then, (a + b) = ?

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Question: A 3-digit number 4a3 is added to another 3-digit number 984 to give a 4-digit number 13b7, which is divisible by 11. Then, (a + b) = ?

[A].

10

[B].

11

[C].

12

[D].

15

Answer: Option A

Explanation:

4 a 3 |
9 8 4 } ==> a + 8 = b ==> b – a = 8
13 b 7 |

Also, 13 b7 is divisible by 11      (7 + 3) – (b + 1) = (9 – b)

  (9 – b) = 0

  b = 9

(b = 9 and a = 1)     (a + b) = 10.

It is being given that (232 + 1) is completely divisible by a whole number. Which of the following numbers is completely divisible by this number?

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Question: It is being given that (232 + 1) is completely divisible by a whole number. Which of the following numbers is completely divisible by this number?
[A].

(216 + 1)

[B].

(216 – 1)

[C].

(7 x 223)

[D].

(296 + 1)

Answer: Option D

Explanation:

Let 232 = x. Then, (232 + 1) = (x + 1).

Let (x + 1) be completely divisible by the natural number N. Then,

(296 + 1) = [(232)3 + 1] = (x3 + 1) = (x + 1)(x2 – x + 1), which is completely divisible by N, since (x + 1) is divisible by N.

8597 – ? = 7429 – 4358

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Question: 8597 – ? = 7429 – 4358

[A].

5426

[B].

5706

[C].

5526

[D].

5476

Answer: Option C

Explanation:

7429 Let 8597 – x = 3071
-4358 Then, x = 8597 – 3071
—- = 5526
3071
—-

What will be remainder when 17200 is divided by 18 ?

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Question:
What will be remainder when 17200 is divided by 18 ?

[A].

17

[B].

16

[C].

1

[D].

2

Answer: Option C

Explanation:

When n is even. (xn – an) is completely divisibly by (x + a)

(17200 – 1200) is completely divisible by (17 + 1), i.e., 18.

   (17200 – 1) is completely divisible by 18.

   On dividing 17200 by 18, we get 1 as remainder.

(xn – an) is completely divisible by (x – a), when

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Question:
(xn – an) is completely divisible by (x – a), when

[A].

n is any natural number

[B].

n is an even natural number

[C].

n is and odd natural number

[D].

n is prime

Answer: Option A

Explanation:

For every natural number n, (xn – an) is completely divisible by (x – a).