Quiz Discussion

A, B, C, D and E sit on five chairs all of which are facing north. C will sit only on the leftmost chair and B will not sit anywhere to the left of A. In how many ways they can be seated?

• 1]

  10

• 2]

  18

• 3]

  36

• 4]

  12

Two variants of the CAT paper are to be given to 12 students. In how many ways can the students be placed in two rows of six each so that there should be no identical variants side by side and that the students sitting one behind the other should have the same variant. Find the number of ways this can be done

• 1]

  2 x ¹²C₆ x (6!)²

• 2]

  2 x 6! x 6!

• 3]

  2 x ¹²C₆ x 6!

• 4]

  None of these

Three unbiased coins are tossed. What is the probability of getting at most two heads ?

• 1]

  3/4

• 2]

  1/4

• 3]

  3/8

• 4]

  7/8

If A, B and C are mutually exclusive and exhaustive events of a random experiment such that P(B)=3/2​P(A) and P(C)=1/2​P(B), then P(A∪C)=

• 1]

  3/13

• 2]

  6/13

• 3]

  7/13

• 4]

  10/13

A box contains 5 green, 4 yellow and 3 white marbles. three marbles are drawn at random. What is the probability that all they are not of the same colour?

• 1]

  3/44

• 2]

  3/55

• 3]

  52/55

• 4]

  41/44

A speaks truth in 75% cases and B in 80% of the cases. In what percentage of the cases are they likely to contradict each other, narrating the same incident?

• 1]

  5%

• 2]

  15%

• 3]

  35%

• 4]

  45%

There are three rooms in a motel: one single, one double, and one for four persons. How many ways are there to house seven persons in these rooms?

• 1]

  7! / 1! 2! 3! 

• 2]

  7! 

• 3]

  7! / 3

• 4]

  7! / 3!

Six boys and 4 girls are to be seated in two separate rows with five chairs each, such that two particular girls are always together and all the girls are not in the same row. In how many ways can they be seated?

• 1]

  15 * 7!

• 2]

  20 * 8!

• 3]

  18 * 7!

• 4]

  (16 * 8! – 4! * 6!)

A box contains two white balls, three black balls and four red balls. Balls of the same colour are distinct. The number of ways in which three balls can be drawn from the box if atleast one black ball is to be included in the draw, is

• 1]

  32

• 2]

  64

• 3]

  128

• 4]

  None Of These

In a lottery, there are 10 prizes and 25 blanks. A lottery is drawn at random. What is the probability of getting a prize?

• 1]

  1/10

• 2]

  2/5

• 3]

  2/7

• 4]

  5/7