swerve wrote: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
The OA is C
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
