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:

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