A salesman makes a 20 percent commission on the selling price of each set

[B BTGModeratorVI]

A salesman makes a 20 percent commission on the selling price of each set of encyclopedias he sells. If he sells 12 identical sets of encyclopedias and makes $1800 in commissions, what is the selling price of each set?

A. $300
B. $600
C. $750
D. $900
E. $1080

Answer: B
Source: GMAT Paper Tests

[S swerve]

A salesman makes a 20 percent commission on the selling price of each set of encyclopedias he sells. If he sells 12 identical sets of encyclopedias and makes $1800 in commissions, what is the selling price of each set?

A. $300
B. $600
C. $750
D. $900
E. $1080

Answer: B
Source: GMAT Paper Tests

\begin{align*}
& 0.20 \cdot 12x = 1800 \\
& 2.40x = 1800 \\
& x = \dfrac{1800}{2.40} \\
& x = 750.
\end{align*}

Check the OA, please.

[Brent@GMATPrepNow]

A salesman makes a 20 percent commission on the selling price of each set of encyclopedias he sells. If he sells 12 identical sets of encyclopedias and makes $1800 in commissions, what is the selling price of each set?

A. $300
B. $600
C. $750
D. $900
E. $1080

Answer: B
Source: GMAT Paper Tests

Let x = the selling price of ONE set of encyclopedias
So, 12x = the TOTAL price of 12 sets of encyclopedias

If the commission is 20%, then the salesman's commission = 20% of 12x
If the salesmen receives $1800 in commissions, we can write: 20% of 12x = $1800
Rewrite as: (0.2)(12x) = $1800

We COULD evaluate (0.2)(12) to get 2.4, but I'd rather not have to divide 1800 by 2.4
Instead, here's what I'd do to speed up the calculations (in my head).

Take: (0.2)(12x) = $1800
Divide both sides by 12 to get: (0.2)(x) = $150
Rewrite 0.2 as 1/5 to get: (1/5)x = $150
Multiply both sides by 5 to get: x = $750

Answer: C

Cheers,
Brent

[Scott@TargetTestPrep]

A salesman makes a 20 percent commission on the selling price of each set of encyclopedias he sells. If he sells 12 identical sets of encyclopedias and makes $1800 in commissions, what is the selling price of each set?

A. $300
B. $600
C. $750
D. $900
E. $1080

Answer: B
Source: GMAT Paper Tests

Letting n = the selling price of one set of encyclopedias, we can create the equation:

0.2(12n) = 1800

2.4n = 1800

n = 750

Answer: C

(Double-check OA, please)