percentage
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A computer typist types a page with 20 lines in 10 minutes but he leaves 8% margin on the left side of the page.Now he has to type 23 pages with 40 lines on each page which he leaves 25% more margin than before.how much time is now required to type these 23 pages?
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Are there answer choices? Here's how I approached it:
1 page, 20 lines, 8% margin, 10 minutes
Of those 20 lines, 8% of the total is blank margin, so the actual amount typed is .92*20=18.4 lines in 10 minutes, or about 1.8 lines per minute.
23 pages, 40 lines, 25% more margin
To figure out out new margin, we simply take the previous amount and add 25% to it: 1.25 * 8 = 10 percent margins.
Using this, we know that 10% of each line is blank, so for 40 lines, the amount typed is 40 * .9 = 36 lines. At a rate of 1.8 lines per minute, each page will take 20 minutes.
All 23 pages will take 23*20 = 460 minutes. Divide by 60 to get to hours and you get 7 2/3 hours.
1 page, 20 lines, 8% margin, 10 minutes
Of those 20 lines, 8% of the total is blank margin, so the actual amount typed is .92*20=18.4 lines in 10 minutes, or about 1.8 lines per minute.
23 pages, 40 lines, 25% more margin
To figure out out new margin, we simply take the previous amount and add 25% to it: 1.25 * 8 = 10 percent margins.
Using this, we know that 10% of each line is blank, so for 40 lines, the amount typed is 40 * .9 = 36 lines. At a rate of 1.8 lines per minute, each page will take 20 minutes.
All 23 pages will take 23*20 = 460 minutes. Divide by 60 to get to hours and you get 7 2/3 hours.
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However, I'd be wary about picking 7 2/3 if it were an option. I rounded from 1.84 lines per minute to 1.8 lines per minute, which means that I used a slightly slower rate and thus got a slightly longer time to complete the work.
If there were an answer like 7 1/2, I would go for that. It is 10 minutes less than 7 2/3, a small change that corresponds to the small rate rounding I did.
If there were an answer like 7 1/2, I would go for that. It is 10 minutes less than 7 2/3, a small change that corresponds to the small rate rounding I did.
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Hi shaanGMAT,
What is the source for this question? The core of this question is built on ratio rules, and while the GMAT will test you several times on the subject of ratios, it won't be in this way. Also, you would have the 5 answer choices to use as reference, so there could very well be a shortcut in the answers that would allow you to avoid some of this math.
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What is the source for this question? The core of this question is built on ratio rules, and while the GMAT will test you several times on the subject of ratios, it won't be in this way. Also, you would have the 5 answer choices to use as reference, so there could very well be a shortcut in the answers that would allow you to avoid some of this math.
GMAT assassins aren't born, they're made,
Rich
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Case 1:shaanGMAT wrote:A computer typist types a page with 20 lines in 10 minutes but he leaves 8% margin on the left side of the page. now he has to type 23 pages with 40 lines on each page which leaves 25% more margin than before. how much time is required to type these 23 pages?
a) 7(1/2) hrs
b) 7(2/3) hrs
c) 23(1/2) hrs
d) 3.916 hrs
Let the length of each line = 100 characters.
Since 8% of the left side constitutes a margin, the margin = (8/100) * 100 = 8.
Thus, the number of characters typed per line = 100-8 = 92.
In 20 lines, the number of characters typed = 20*92 = 20*92.
Since the time = 10 minutes, the rate = (20*92)/10 = (2*92) characters per minute.
Case 2:
Since 25% MORE of the left side constitutes a margin, the new margin = 8 + (1/4)8 = 10.
Thus, the number of characters typed per line = 100-10 = 90.
In 40 lines, the number of characters typed = 40*90.
In 23 pages, the number of characters typed = 40*90*23.
At a rate of (2*92) characters per minute, the time required = (40*90*23)/(2*92) = 450 minutes = 7.5 hours.
The correct answer is A.
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I followed the following approach:
Assuming every line has 100 characters.
=> with 8% margin, the total number of characters written in one line is 100-8 = 92
Time taken to write 20 lines is 10 mins
=> time taken to write 1 line = 92 characters is 10/(92*20)
Now, when the margin is increased by 25% => new margin is 8+ 0.25*8 = 10
=> number of characters per line now = 90
Total number of characters to be written = number of characters per line * number of lines per page * number of pages = 90*40*23
Total time required = total number of characters * time required to type one character
= (90*40*23)*(10/(92*20)) = 450 minutes = 7 hours and 30 minutes
I guess the key to this question was to break the number of lines into the number of characters so that both the cases have a common decision making variable.
Cheers!
Assuming every line has 100 characters.
=> with 8% margin, the total number of characters written in one line is 100-8 = 92
Time taken to write 20 lines is 10 mins
=> time taken to write 1 line = 92 characters is 10/(92*20)
Now, when the margin is increased by 25% => new margin is 8+ 0.25*8 = 10
=> number of characters per line now = 90
Total number of characters to be written = number of characters per line * number of lines per page * number of pages = 90*40*23
Total time required = total number of characters * time required to type one character
= (90*40*23)*(10/(92*20)) = 450 minutes = 7 hours and 30 minutes
I guess the key to this question was to break the number of lines into the number of characters so that both the cases have a common decision making variable.
Cheers!