If p varies directly as d, and p = 42 when d = 7, find p when d = 21.?

Question

A.
p = 126

B.
p = 88

C.
p = 163

D.
p = 14

please help! Thank You

Answer 1

Since p varies directly as d, p/d = constant = 42/7 = 6

So, when d = 21, p = 6 X 21 = 126.

So, a is the right answer.

Answer 2

p varies directly as d
Therefore p=kd where k is the variation constant
Given p=42 when d=7
Hence 42=k*7
or k=42/7=6
So when d=21.
p=k*d
=6*21
=126

Answer 3

p = kd, k = p/d

In this case, when p = 42, d = 7, so k = 42/7 = 6

So p = 6d

So when d = 21, p = 21 * 6 = 126

Ans: A

Answer 4

ratio problem: p/d = 42/7
when d = 21.......same as saying 42 is to 7 and p is to 21

42/7=p/21

p = 126