If 2^a = b then 8^a must equal to

Question

A. b^3
B. b^2
C. 3b
D. b^(2a)
E. b^(3a)

hopeful101candidate · Answer

I would pick simple numbers to solve this. Say a = 2, then b = 2^2 = 4, so 8^2 = 64. Check the solutions:

A. b^3 = 4^3 = 64, which is what we're looking for. 
B. b^2 = 16, not correct
C. 3b = 12, not correct
D. b^(2a) = 256, not correct
E. b^(3a) = 4096, not correct

Answer is A.

g106 · Answer

2^a = b

8^a = 2^3a = 2^(a*3) = b^3

Ans A

PareshGmat · Answer

Answer = A. b^3

2^a = b

(2^a)^3 = b^3

2^{3a} = b^3

(2^3)^a = b^3

8^a = b^3

Viver · Answer

Best approach in such queries is to look for each answers, we know we cannot substitute the value of a in 8^a from 2^a = b. 
So , we go to answers straight. 
look for options- A says b^3 which is 2^a ^3 = 8^a. 
So in this case we dont look further and go to the right answer which option A.

When questions and answers both are in variable in PS, subtituting with numbers such as 2/3, may not be a quick idea.

vedavyas9 · Answer

2^a = b

apply 3rd power on both sides => (2^a)^3 = b^3
 => (2^3)^a = b^3
 => 8^a = b^3

Bunuel · Answer

OFFICIAL SOLUTION:

(A) 8ª = (2³)ª = 2³ª = (2ª)³

Since 2ª = b then (2ª)³ = b³, choice (A).

ScottTargetTestPrep · Answer

Since 8^a = (2^3)^a = (2^a)^3 and 2^a = b, 8^a = b^3.

Answer: A

Mo2men · Answer

Let a =2...then 2^2 = 4

8^a = 8^2 =64 = 4^3 = b^3

Answer: A

AkshdeepS · Answer

2^a = b ------(I)

8^a

(2^3)^a

(2^a)^3

Replace  2^a  with "b" as per equation (I)

b^3

(A)

bumpbot · Answer

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If 2^a = b then 8^a must equal to

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