a is directly proportional to b. If a = 8 when b = 2, what is a when b

Question

a is directly proportional to b. If a = 8 when b = 2, what is a when b = 4?

(A) 10
(B) 16
(C) 32
(D) 64
(E) 128

D3N0 · Answer

ans: B

Once again a/b = A/B so
8/2=A/4 so A=16 ans.

Ans: B

pushpitkc · Answer

When a is directly proportional to b, we can say that a = kb where k is a constant.

We are told that if a = 8, b = 2. Now, 8 = k*2 -> Constant(k) = 4

Therefore, the value of a = kb = 4*4 =  16(Option B)  when b = 4.

EgmatQuantExpert · Answer

Solution

Given:  
 • a is directly proportional to b
• When b = 2, a = 8

To find:  
 • The value of a, when b = 4

Approach and Working:   
As a is directly proportional to b, a = k * b, where k is a constant

Given that, when b = 2, a = 8
 • Therefore, we can write 8 = k * 2
Or, k = 4

• Hence, a = 4b

When b = 4,
 • a = 4 * 4 = 16

Hence, the correct answer is option B.

Answer: B

KSBGC · Answer

Note : a is directly proportional to b.

a is 8 when b is 2. It means a will be 4 times larger than b all time.

Now b is 4. what is a ?

4 times of b will be 16.

Thus the best answer is B.

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