100+ Number System Questions for Bank PO Exams Pdf - 1

Question: 1

The digit in the unit’s place of the number 12399 is

(A) 1

(B) 2

(C) 3

(D) 7

Ans: D

34 gives unit digit 1.

So, (34)24 gives unit digit 1.

And, 33 gives unit digit 7.

∴ 399 = (34)24 × 33 gives unit digit (1 x 7) i.e. 7.

Question: 2

If n be any natural number then by which largest number (n3 - n) is always divisible?

(A) 3

(B) 6

(C) 12

(D) 18

Ans: B

(13 - 1) = 0, (23 - 2) = 6, (33 - 3) = 24, (43 - 4) = 60 and so on, each one of which is divisible by 6.

Question: 3

The sum of four consecutive even numbers A, B, C and D is 180. What is the sum of the set of next four consecutive even numbers?

(A) 169

(B) 204

(C) 212

(D) 214

Ans: C

Let the four consecutive even numbers be a, a + 2, a + 4 and a + 6.

Then, a + a + 2 + a + 4 + a + 6 = 180 ⇒ 4a = 168 ⇒ a= 42.

So, these numbers are 42, 44, 46 and 48.

Sum of next four consecutive even numbers = (50 + 52 + 54 + 56) = 212.

Question: 4

106 x 106 – 94 x 94 = ?

(A) 1904

(B) 1906

(C) 2200

(D) 2400

Ans: D

(106 × 106 - 94 × 94)

= (106)2 - (94)2= (106 + 94) (106 - 94) = (200 × 12) = 2400.

Question: 5

(24 + 25 + 26)2 - (10 + 20 + 25)2 = ?

(A) 352

(B) 752

(C) 2600

(D) 2800

Ans: C

(24 + 25 + 26)2 - (10 + 20 + 25)2 = (75)2 - (55)2

= (75 + 55) (75 - 55) = (130 × 20) = 2600.

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