100+ Surds and Indices Aptitude Questions and Answers - 1

Question: 1

[43 × 54] ÷ 45 = ?

(A) 39.0625

(B) 35.6015

(C) 30.0925

(D) 29.0825

Ans: A

$${4^3 × 5^4 } / {4^5 }$$ = $${5^4 } /{4^(5 – 3)}$$ = $${5^4 } /{4^2} $$ = $${625} / {16}$$ = 39.0625.

Question: 2

(10)24 × (10)-21 = ?

(A) 10

(B) 100

(C) 1000

(D) 10000

Ans: C

(10)24 × (10)-21 = 10(24 - 21) = 103 = 1000.

Question: 3

If 5a = 3125, then the value of 51 - 3 is

(A) 15

(B) 25

(C) 125

(D) 625

Ans: B

5a = 3125 = 55⇒ a = 5 ⇒ 5(a – 3) = 5(5 - 3) = 52 = 25.

Question: 4

If m and n are whole numbers such that mn = 121, then the value of (m – 1)n + 1 is

(A) 1

(B) 10

(C) 100

(D) 1000

Ans: D

We know that 112 = 121.

Putting m = 11 and n = 2, we get

(m – 1)n + 1 = (11 - 1)(2 + 1) = 103 = 1000.

Question: 5

50 × 8 = ?

(B) 5

(C) 8

(D) 40

Ans: C

50 × 8 = 1 × 8 = 8. [∴ 50 = 1]

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