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gcf101 · 09-10-2005, 09:56 PM

1.
SAT-specific shortcut.
Let's assume k equal some reasonable, say, $10.
Answers a, b, and e don't make sense,
c should be out because it features 1,000 - a number from the question.
That leaves d.

2.
Slightly more "scientific" approach.
Every day: $k in, $k/3 out, so Dwayne pockets $(k-k/3) per day.
In x days (k-k/3)*x = 1000, so x = 1000/something, where something is not k.
Only 1500/k fits this criteria, c is the answer.

3.
Math-ly correct:
(k-k/3)*x = 1000
k(1 - 1/3)*x = 1000
x * k * 2/3 = 1000
x = (1000 * 3 / 2) / 2k = 1500 / k.

09-10-2005, 09:56 PM	#5
gcf101 Moderator Join Date: Jun 2005 Location: Northeast Gender: Not Saying Threads: 28 Posts: 949	p409 question #7 - my 2 cents (or k dollars) 1. SAT-specific shortcut. Let's assume k equal some reasonable, say, $10. Answers a, b, and e don't make sense, c should be out because it features 1,000 - a number from the question. That leaves d. 2. Slightly more "scientific" approach. Every day: $k in, $k/3 out, so Dwayne pockets $(k-k/3) per day. In x days (k-k/3)x = 1000, so x = 1000/something, where something is not k. Only 1500/k fits this criteria, c is the answer. 3. Math-ly correct: (k-k/3)x = 1000 k(1 - 1/3)x = 1000 x k * 2/3 = 1000 x = (1000 * 3 / 2) / 2k = 1500 / k.