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PLEASE EXPLAIN DS#79 IN 12TH EDITION REVIEW BOOK (PG#315)
Source: Beat The GMAT — Data Sufficiency |
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neerajkumar1_1
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Geva@EconomistGMAT
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Two options to buy a computer:clinton wrote:I need help!!!
p1 dollars +sales tax of t1 percent,
Or
P2 dollars + sales tax of t2 percent.
Is the total cost of the computer greater in the first case than in the second?
(1) t1>t2
(2) p1t1 > p2t2
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Geva@EconomistGMAT
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the solution method is just as the OG says - plug in numbers. The secret is to make the separation between the numbers t1 and t2, and what the numbers stand for (i.e. percents).Geva Stern wrote:Two options to buy a computer:clinton wrote:I need help!!!
p1 dollars +sales tax of t1 percent,
Or
P2 dollars + sales tax of t2 percent.
Is the total cost of the computer greater in the first case than in the second?
(1) t1>t2
(2) p1t1 > p2t2
For stat. (1), we have no clue what's the price of the computers. Plug in t1=10, t2=5, for example, but the final result will depend on the cost of the computers:
If P1=$100, then P1+tax will equal 100 + 10% of 100 = $110
If P2 is then also equal to $100, then P2+tax will equal 100+5% of 100 = $105, and A>B
But if P2 costs $200, then P2+tax will equal 200+5% of 200 = $210, and A<B.
Insufficient.
(2) This one is trickier, but remember:
when you're plugging in t1=10, you're not plugging in t1=10% - just t1=10.
Thus, using our original plug ins:
p1*t1 = 100*10 = 1000 (note - we're multiplying by t1=10, not 10 percent - that's what the statement says, so that's what we stick to)
p2*t2 = 100*5 = 500
we've already seen that in this case the prices are $100 and $105, and A>B.
for a second plug in, try to break this pattern while still conforming to the statement: you want a small P1 and and a large t1, so that P1*t1 is still greater than p2*t2, but the move to percents will result with a small price for A.
Take p1=10 and t1 = 100, so that p1*t1 is still 10*100 = 1000 (which is greater than p2*t2=500, satisfying the statements)
But the minute we move to percents, we get that the price of computer A is now $10 + 100% of 10 = $10+$10 = $20 - much smaller than the $105 price of B. A<B, so stat. (2) is insufficient.
since t1=100 is greater than t2=5, this case also satisfies stat. (1), meaning that both statements combined still allow both A>B and A<B - answer is E.
Thank you!
I have one follow up question for the GMAT experts.
Just to be clear, the Official Guide 12th edition is misprinted, yes? In my book on p315 it says P1(1+ T1/0)? I believe the equation should be P1(1+ T1/100).
I have one follow up question for the GMAT experts.
Just to be clear, the Official Guide 12th edition is misprinted, yes? In my book on p315 it says P1(1+ T1/0)? I believe the equation should be P1(1+ T1/100).
GMAT/MBA Expert
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Brent@GMATPrepNow
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Yes, the equation should be P1(1+ T1/100)bynddrvn wrote:Thank you!
I have one follow up question for the GMAT experts.
Just to be clear, the Official Guide 12th edition is misprinted, yes? In my book on p315 it says P1(1+ T1/0)? I believe the equation should be P1(1+ T1/100).
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
