irida wrote:
To settle mutual debts, two gamblers agree that phones are worth $300 each and that watches are worth $210 each. When one gambler owes money to the other, he settles the debt in phones and/or watches, with “balance” received in the form of phones or watches as well (For example, a $480 debt could be paid with three phones, with two watches received in balance). What is the smallest amount of debt that can be settled in this way? A) 10 B) 30 C) 50 D) 70 E) 90
I am quite confused on the amount of money---from the statement, the minimum should be 210 (the watch's price)? But all of the 5 answers are below 210.
How to solve the problem? Seek advise.
Notice the example they have given. 480 debt can be paid with 3 phone (total = $900) with receiving 2 watches is balance (receiving $420).
900 - 420 = 480
So to pay a debt of $90, one would need to give a phone ($300) and receive a watch ($210). In effect, one would have paid 300 - 210 = $90
We need a multiple of 300 to be as close as possible to a multiple of 210.
300 -> 600, 900, 1200, 1500, 1800, 2100, 2400, 2700 ...
210 -> 420, 630, 840, 1050, 1260, 1470, 1680, 1890, 2100 ...
So you can settle a debt of $30 by paying 5 phones ($1500) and receiving 7 watches in return ($1470).