How many answers correct?

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How many answers correct?

by tonebeeze » Fri Mar 11, 2011 10:59 am
A certain tests consists 8 sections with 25 questions, numbered from 1 to 25, in each section. If a student answered all of the even-numbered questions correctly and 3/4 of the odd-numbered questions correctly, what was the total number of questions he answered correctly?

a. 150
b. 172
c. 174
d. 175
e. 176

OA = C

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by anshumishra » Fri Mar 11, 2011 11:17 am
tonebeeze wrote:A certain tests consists 8 sections with 25 questions, numbered from 1 to 25, in each section. If a student answered all of the even-numbered questions correctly and 3/4 of the odd-numbered questions correctly, what was the total number of questions he answered correctly?

a. 150
b. 172
c. 174
d. 175
e. 176

OA = C
1-25 -> 13 odd, 12 even

So, total no. of questions answered correctly = 12*8 + 13*8*3/4 = 96+78 = 174 C
Thanks
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by GMATGuruNY » Fri Mar 11, 2011 2:03 pm
tonebeeze wrote:A certain tests consists 8 sections with 25 questions, numbered from 1 to 25, in each section. If a student answered all of the even-numbered questions correctly and 3/4 of the odd-numbered questions correctly, what was the total number of questions he answered correctly?

a. 150
b. 172
c. 174
d. 175
e. 176

OA = C
To count the number of evenly spaced integers in a set:

Number of integers = (Biggest - Smallest)/(distance between each successive pair) + 1

Number of even integers from 2 to 24 inclusive = (24-2)/2 + 1 = 12.
Number of odd integers from 1 to 25 inclusive = (25-1)/2 + 1 = 13.
Answered correctly in the 8 sections:
8*12 = 96 even questions.
(3/4)*8*13 = 78 odd questions.
96+78 = 174.

The correct answer is C.
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