Problem Solving

BTGmoderatorLU wrote:Source: GMAT Prep

If a certain wheel turns at a constant rate of \(x\) revolutions per minute, how many revolutions will the wheel make in \(k\) seconds?

A. \(60kx\)

B. \(kx\)

C. \(\frac{x}{k}\)

D. \(\frac{x}{60k}\)

E. \(\frac{kx}{60}\)

The OA is E

We can solve the question using equivalent ratios

Wheel turns at a constant rate of x revolutions per minute
We can also say the wheel turns at a constant rate of x revolutions per 60 seconds
In other words, # of revolutions/seconds elapsed = x/60

How many revolutions will the wheel make in k seconds?
Let R = the number of revolutions will the wheel make in k seconds
We can now write: x/60 = R/k
To solve for R, we can first cross multiply to get: 60R = kx
Divide both sides by 60 to get: kx/60

Answer: E

BTGmoderatorLU wrote:Source: GMAT Prep

If a certain wheel turns at a constant rate of \(x\) revolutions per minute, how many revolutions will the wheel make in \(k\) seconds?

A. \(60kx\)

B. \(kx\)

C. \(\frac{x}{k}\)

D. \(\frac{x}{60k}\)

E. \(\frac{kx}{60}\)

The OA is E

Since k seconds is k/60 minutes, the wheel will make x * k/60 = xk/60 revolutions in k seconds.

Alternate Solution:

We can create a proportion: "x revolutions is to 60 seconds as q revolutions is to k seconds," and our goal is to solve for q:

x/60 = q/k

xk = 60q

xk/60 = q

Answer: E

BTGmoderatorLU wrote:Source: GMAT Prep

If a certain wheel turns at a constant rate of \(x\) revolutions per minute, how many revolutions will the wheel make in \(k\) seconds?

A. \(60kx\)

B. \(kx\)

C. \(\frac{x}{k}\)

D. \(\frac{x}{60k}\)

E. \(\frac{kx}{60}\)

The OA is E

Since k seconds is k/60 minutes, the wheel will make x * k/60 = xk/60 revolutions in k seconds.

Alternate Solution:

We can create a proportion: "x revolutions is to 60 seconds as q revolutions is to k seconds," and our goal is to solve for q:

x/60 = q/k

xk = 60q

xk/60 = q

Answer: E