gurudabl wrote:
Hi experts,
Bunuel EMPOWERgmatRichC GMATinsight JeffTargetTestPrepw^2 + 250 w - 15000 = 0
It's hard to determine the value of w by doing a straight forward factorization. Therefore, can we use a reverse approach?
p * -q = -15,000 and p - q = 250
(w+p) (w-q)
w = -p and w = q --> This positive root is already given to us in the answer option. Therefore, the other root will be p * -50 = -15, 000 which will give us p = 300
300 -50 = 250 Satisfies the other equation as well.
Therefore, the answer is 50.
Please confirm.
Thank you.
Hi gurudabl,
Your approach to this question works fine. I would not go so far as to say that it's necessarily a 'faster' approach though. Factoring the 15,000 might seem a little 'scary' at first, but we have a LOT of clues to work with:
1) We know that we're dealing with integers - and the answers are fairly 'nice' numbers to work with, so the solution will probably be a nice, round number.
2) From the Quadratic, we know that we'll have one positive and one negative number - and the SUM will be +250.
3) With the "15" in 15,000 we're probably going to have either 1x15 or 3x5, and then it's just a matter of distributing the three "0"s.
Since the sum is +250, it would make sense to place two of the "0s" with a 3...... so we have +300 - and with the remaining 'pieces' (the 5 and the third "0") we have 50....
+300 and -50 is +250, which is an exact match for what's in the equation (and which gives us the two roots).
GMAT assassins aren't born, they're made,
Rich
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