gmat prep

[hey_thr67]

OA is D

[Anurag@Gurome]

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 once, 10 were revised twice, and the rest required no revisions, what was the total cost of having the manuscript typed?

Typing cost of 100 pages = 5*100 = $500
Single revision cost of 40 pages = 1*3*40 = $120
Double revision cost of 10 pages = 2*3*10 = $60

Hence, total cost of having the manuscript typed = $(500 + 120 + 60) = $680

The correct answer is D.

[hey_thr67]

But I am mistaking at counting. There are 60 pages that won't be repeated So for them 60x5= 300

Now the 40 that repeat are in those 60 right. So, 40*3= 120. Also, 10 are those in 40 so, 10*3 = 30

Hence, Ans according to me is 450. Where am I getting wrong ?

[Anurag@Gurome]

But I am mistaking at counting. There are 60 pages that won't be repeated So for them 60x5= 300

Now the 40 that repeat are in those 60 right. So, 40*3= 120. Also, 10 are those in 40 so, 10*3 = 30

Hence, Ans according to me is 450. Where am I getting wrong ?

First of all all page has to be typed before it can be revised.
Hence, you have to type all the 100 pages which will cost 5*100 = $500

And in general, when a question says "40 were revised once, 10 were revised twice," this means the double revised 10 pages are not included in the single revised ones. Once you have revised 10 pages twice you cannot claim them as single revised ones. This is because we don't know the order of the revisions.

If it was mentioned that 40 pages were revised first and then 10 pages required one more revision, then you solution would have made sense.

Hope that helps.