A store purchased 100 balls from a wholesaler. Initially, th

[Max@Math Revolution]

[GMAT math practice question]

A store purchased 100 balls from a wholesaler. Initially, they sold them for the unit cost price plus 30%. After selling 70 balls at this price, they reduced the selling price by $15 and sold the remaining 30 balls at this marked-down price. The total profit made after selling all 100 balls was $2,400. What was the original unit cost of each ball?

A. $85
B. $90
C. $95
D. $100
E. $105

[Max@Math Revolution]

=>

Let x be the unit cost of each ball.
Then 70 * x * 1.3 + 30*( x*1.3 - 15 ) = 100x + 2,400.
Solving for x yields
130*x - 450 = 100*x + 2400,
And
30x = 2850.
Dividing both sides by 30 gives x = 95.

Therefore, C is the answer.
Answer: C