Hi iNumbv,
The math involved in this question can be done in a variety of ways; it's just a matter of what method you find most comfortable.
Here, we're told that a person bought 150 packets of chocolate...
We can say that 1 packet cost $X
We then sell 50 each at....
a 5% profit = 1.05X each
a 0% profit = 1X each
a 10% loss = .9X each
Since the question focuses on the net profit or loss, we can ignore the 50 packets we sold for a 0% profit and focus on the other 100.
50(1.05X + .9X) =
50(1.95X)
IF we had 50(2X), then we would have 0 profit.
Here we have 50(1.95X), so we clearly lost money.
The .05X that we lost can be quantified as 50(.05X) = 2.5X
Once we know the purchase price (X) of each packet, then we can just plug in and we'll know the total loss.
We're told that the price of a "10% loss" packet = $9, so the original price = $10. We can plug that in for X...
2.5(10) = 25 dollars lost
Final Answer:
GMAT assassins aren't born, they're made,
Rich