Skip to main content

Aptitude Day 146

Problems on Probability:

1. A box contains 10 electric bulbs, out of which 3 is defective. 2 bulbs are chosen at random from this box. The probability that at least one of these is defective, is:

Solution:
                 n(S) = 10C2 =  45

                  n(E) = 7C2  = 21.
                      
                  P(none is defective) = n(E)/ n(S)
                                                   = 21/45
                                                   = 7/15.

                  P(at least one is defective) = 1- 7/15
                                                             = 8/15.

2. In class, 40% of the students English, 30% offered French and 20% offered both. If a student is selected at random. What’s the probability that he has offered both English and French?

Solution:
                 P(AUB) = P(A)+P(B)-P(A∩B)
                               = 40/100+30/100-20/100
                               = 50/100
                               = 1/2.

Comments

Post a Comment

Popular posts from this blog

Aptitude Day 59

Answers of Day 58:     1. 1/90.     2. 20 Problems to solve: 1. The product of two numbers is 33 and the sum of their squares is 130. Find their difference. 2. The sum of two numbers is 100 and their difference is 20. Find their product.
Post a Comment
Read more

Aptitude Day 47

Problem On Numbers 1. Three numbers are in the ratio 1:2:3 and their average is 180. What's the largest number? Solution:                 Let the numbers be x, 2x and 3x.                 x+2x+3x = 180                          6x = 180                            x = 30                The largest number is 3x = 90. Problem to solve: Three numbers are in the ratio of 4:2:3 and their product is 648. Find the smallest number. 
Post a Comment
Read more