woohoo921 wrote:
Bunuel wrote:
A garden center sells a certain grass seed in 5-pound bags at $13.85 per bag, 10-pound bags at $20.43 per bag, and 25-pound bags $32.25 per bag. If a customer is to buy at least 65 pounds of the grass seed, but no more than 80 pounds, what is the least possible cost of the grass seed that the customer will buy?
A) $94.03
B) $96.75
C) $98.78
D) $102.07
E) $105.3
BunuelI fell for the trap and thought that getting exactly 65 pounds would be the most cost effective (starting with using 2 bags of 25 pounds, then 1 10-pound bag, and 1 5-pound bag). If you were approaching this from a fresh start, would you have first maximized the number of the 25 bags (so 3 bags) and then compared it to the original calculation I did of trying to find 65 pounds?
I am just trying to think of how someone would have laid this out strategically without wasting too much time fidgeting with the numbers.
Thanks for your help!
Hi woohoo921,
It's important to remember that nothing about a GMAT question is ever 'random' - all of the words and numbers are carefully chosen, so it's often beneficial to think in terms of "why" (re: WHY was I told this specific piece of information?). We're asked, if a customer is to buy AT LEAST 65 pounds of the grass seed, but NO MORE THAN 80 pounds, what is the LEAST possible cost of the grass seed that the customer could buy.
Many Test Takers would focus on buying exactly 65 pounds of seed, but the question did NOT ask for the cost of 65 pounds of seed; it asked for the LEAST amount you could spend while buying "AT LEAST 65 pounds... but NO MORE THAN 80 pounds." That wording should make you consider whether you've actually spent the LEAST amount possible or not (and whether you should be focused on 65 pounds or some other total...).
With a quick comparison of the three prices, you should notice that 10-pound bag costs LESS than two 5-pound bags and a 25-pound bag costs LESS than two 10-pound bags. Thus, the lowest price-per-pound occurs when we buy 25-pound bags of seed.
To hit 65 pounds exactly, we have to buy 4 bags (including 2 that are more costly per pound). With 75 pounds though, we can buy just 3 of the 25-pound bags - and get the LOWEST price-per-pound. THAT is the actual lowest price possible.
GMAT assassins aren't born, they're made,
Rich
Contact Rich at: Rich.C@empowergmat.com