Official Quant thread for CAT 2013

khannaiim · March 21, 2013, 5:20am

@jain4444 said:
A cube has 8 vertices. For each pair of distinct vertices, we connect them up with a line segment. There are C(8 , 2) = 28 such line segments. For each of these 28 line segments, we mark the midpoint. How many distinct points have been marked as the midpoints ?

19.this question has been done before.

tusharrr · March 21, 2013, 5:22am

@KhannaiiM yes i have asked

the_loser · March 21, 2013, 5:53am

@Subhashdec2 said:
28-6-3=19??

what's this 6 & 3 subtracted for.?

dexian · March 21, 2013, 5:57am

@The_Loser said:
what's this 6 & 3 subtracted for.?

on each of the 6 faces two diagonals will bisect each other so there is a common point, so minus 6.
now consider body diagonals... there will be 4 of them and all will meet at the same point . so minus 3

subhashdec2 · March 21, 2013, 5:57am

@The_Loser said:
what's this 6 & 3 subtracted for.?

3 for body diagnols(there will be 4 in total)

1 each for the face diagnol 1*6=6

jain4444 · March 21, 2013, 6:36am

ABCD is a square where M and N are midpoints of AD and CD, respectively. If sin ˆ MBN=a/b, where a and b are coprime positive integers, what is the value of a+b?

scrabbler · March 21, 2013, 6:42am

@jain4444 said:
ABCD is a square where M and N are midpoints of AD and CD, respectively. If sin ˆ MBN=a/b, where a and b are coprime positive integers, what is the value of a+b?

8? I get 3/5...

regards
scrabbler

heylady · March 21, 2013, 6:45am

@jain4444 said:
ABCD is a square where M and N are midpoints of AD and CD, respectively. If sin ˆ MBN=a/b, where a and b are coprime positive integers, what is the value of a+b?

8?

gnehagarg · March 21, 2013, 6:45am

@jain4444 said:
ABCD is a square where M and N are midpoints of AD and CD, respectively. If sin ˆ MBN=a/b, where a and b are coprime positive integers, what is the value of a+b?

Let side of square be a

NB=rt(5)*a/2
MB=rt(5)*a/2
MN=rt(2)*a/2

Apply cosine law
cos/_MBN=4/5
Sin/_MBN=3/5

a+b=8

dexian · March 21, 2013, 6:51am

@jain4444 said:
ABCD is a square where M and N are midpoints of AD and CD, respectively. If sin ˆ MBN=a/b, where a and b are coprime positive integers, what is the value of a+b?

3/5
a+b=8

albiesriram · March 21, 2013, 7:21am

A speaks truth in 60% of the cases and b in 90% of the cases. In what percentage of cases are they likely to contradict each other in stating the same fact?

scrabbler · March 21, 2013, 7:23am

@albiesriram said:
A speaks truth in 60% of the cases and b in 90% of the cases. In what percentage of cases are they likely to contradict each other in stating the same fact?

42%?

.6 *.1 + .9 * .4

regards
scrabbler

dushyantagarwal · March 21, 2013, 7:26am

@albiesriram said:
A speaks truth in 60% of the cases and b in 90% of the cases. In what percentage of cases are they likely to contradict each other in stating the same fact?

((60 * 10) + (40 * 90))/100 = 42% ?

dexian · March 21, 2013, 7:29am

@albiesriram said:
A speaks truth in 60% of the cases and b in 90% of the cases. In what percentage of cases are they likely to contradict each other in stating the same fact?

1 - (.6*.9 + .1 * .4)= .42

albiesriram · March 21, 2013, 7:35am

dexian · March 21, 2013, 7:38am

@albiesriram said:

D

albiesriram · March 21, 2013, 7:41am

@Dexian said:
D

OA says B.

heylady · March 21, 2013, 7:50am

@albiesriram said:

B.....

karangarcia · March 21, 2013, 7:54am

What is the approach to this problem???

techgeek2050 · March 21, 2013, 7:58am

@KaranGarcia said:
What is the approach to this problem???

9! / (6!)( 3!) = 84