PROBABILITY
∴ Probability of 2 students having the same
birthday is 0.008
probability of 2 Students not having the same
Sol.
There are two events in this sum
1st Event
2nd Event
Since 2 students having same birthday and 2 students not having same birthday are two complementary events
We know sum of probabilities of two complementary events is 1.
0.992
Q. A box contains 5 red marbles, 8 white marbles and 4 green marbles. One marble is taken out of the box at random. What is the probability that the marble taken out will be
(i) red ? (ii) white ? (iii) not green?
As the box contains 5 red marbles, 8 white marbles and 4
green marbles
Total no of possible outcomes =
(i) Let A be the event that a red marble is drawn
∴ No. of outcomes favourable to A = 5
Sol.
5 + 8 + 4
Total number of marbles present in the box
How many red marbles are there?
∴ P (A) =
5
17
As the box contains
= 17
Not green means either it will be red or it can be white but it should not be green
(iii) Let C be the event that the marble drawn is not green
∴ No of outcomes favourable to C = 13
(ii) Let B be the event that a white marble is drawn
∴ No of outcomes favourable to B = 8
Q. A box contains 5 red marbles, 8 white marbles and 4 green marbles. One marble is taken out of the box at random. What is the probability that the marble taken out will be
(i) red ? (ii) white ? (iii) not green?
Sol.
How many white marbles are there?
5 + 8 = 13
∴ P (B) =
∴ P (C) =
8
13
Total no. of. possible outcomes
= 5
+ 8
+ 4
= 17
17
Total no. of. possible outcomes
= 5
+ 8
+ 4
= 17
17