Manuscript Cost Problem(What am I missing)

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Found this on a practice test, seems easy but I still can't understand where I'm wrong

Rates for having a manuscript typed at a certain typing service are $5 per page for the first time a page is typed and $3 per page each time a page is revised. If a certain manuscript has 100 pages, of which 40 were revised only once, 10 were revised twice, and the rest required no revision, what was the total cost of having the manuscript typed

a) 430
b) 620
c) 650
d) 680
e) 770

Answer is D
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My answer choice was 650, but I was marked wrong for it.

100*5=500 (for the 100 pages typed for the first time)
40*3=120 (for the first round of revisions)
10*3=30 (for the ten pages revised twice)

500+120+30=650, Where am I wrong? Am I just missing something here?[/spoiler]
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by niketdoshi123 » Thu Jul 12, 2012 8:47 pm
jdciaravino wrote:Found this on a practice test, seems easy but I still can't understand where I'm wrong

Rates for having a manuscript typed at a certain typing service are $5 per page for the first time a page is typed and $3 per page each time a page is revised. If a certain manuscript has 100 pages, of which 40 were revised only once, 10 were revised twice, and the rest required no revision, what was the total cost of having the manuscript typed

a) 430
b) 620
c) 650
d) 680
e) 770

Answer is D
.
.
.
.
.
.
.
.
My answer choice was 650, but I was marked wrong for it.

100*5=500 (for the 100 pages typed for the first time)
40*3=120 (for the first round of revisions)
10*3=30 (for the ten pages revised twice)this has to be 10*3*2 = 60 [ because they are revised twice]

500+120+60=680, [/spoiler]
I hope its clear now

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by jdciaravino » Thu Jul 12, 2012 9:51 pm
ah, I had mistakenly assumed that the 10 twice revised pages were taken out of the 40 that were revised once. careless errors. GMAT lesson learned, never assume anything that isn't explicitly stated. Thank you niket