Probability Ex 15.1 Solutions
Question - 11 : - Gopi buys a fishfrom a shop for his aquarium. The shopkeeper takes out one fish at random froma tank containing 5 male fish and 8 female fish (see Fig. 15.4).
Answer - 11 : -
What is the probability that the fish taken out is a male fish?
Question - 12 : - A game of chanceconsists of spinning an arrow which comes to rest pointing at one of thenumbers 1, 2, 3, 4, 5, 6, 7, 8 (see Fig. 15.5), and these are equally likelyoutcomes.
Answer - 12 : -
What is the probability that it will point at
(i) 8?
(ii) an odd number?
(iii) a number greater than 2?
(iv) a number less than 9?
Question - 13 : - A die is thrownonce. Find the probability of getting
Answer - 13 : -
(i) a prime number;
(ii) a number lying between 2 and 6;
(iii) an odd number.
Solution:
Total possible events when a dice is thrown =6 (1, 2, 3, 4, 5, and 6)
P(E) = (Number of favourable outcomes/ Totalnumber of outcomes)
(i) Total number of prime numbers = 3 (2, 3 and 5)
P (getting a prime number) = 3/6 = ½ = 0.5
(ii) Total numbers lying between 2 and 6 = 3 (3, 4 and 5)
P (getting a number between 2 and 6) = 3/6 = ½= 0.5
(iii) Total number of odd numbers = 3 (1, 3 and 5)
P (getting an odd number) = 3/6 = ½ = 0.5
Question - 14 : - One card is drawnfrom a well-shuffled deck of 52 cards. Find the probability of getting
Answer - 14 : -
(i) a king of red colour
(ii) a face card
(iii) a red face card
(iv) the jack of hearts
(v) a spade
(vi) the queen of diamonds
Five cards the ten,jack, queen, king and ace of diamonds, are well-shuffled with their facedownwards. One card is then picked up at random.
Answer - 15 : -
(i) What is the probability that the card is the queen?
(ii) If the queen is drawn and put aside, what is the probability that the second card picked up is (a) an ace? (b) a queen?
12 defective pensare accidentally mixed with 132 good ones. It is not possible to just look at apen and tell whether or not it is defective. One pen is taken out at randomfrom this lot. Determine the probability that the pen taken out is a good one.
Answer - 16 : - 
Question - 17 : - (i) A lot of 20bulbs contain 4 defective ones. One bulb is drawn at random from the lot. Whatis the probability that this bulb is defective?
Answer - 17 : -
(ii) Suppose the bulb drawn in (i) is not defective and is not replaced. Now one bulb is drawn at random from the rest. What is the probability that this bulb is not defective?
Question - 18 : - A box contains 90discs which are numbered from 1 to 90. If one disc is drawn at random from thebox,
Answer - 18 : -
find the probability that it bears
(i) a two-digit number
(ii) a perfect square number
(iii) a number divisible by 5.
Question - 19 : - A child has a diewhose six faces show the letters as given below:
Answer - 19 : - 
The die is thrownonce. What is the probability of getting
(i) A?
(ii) D?
Suppose you drop adie at random on the rectangular region shown in Fig. 15.6. What is theprobability that it will land inside the circle with diameter 1m?
Answer - 20 : - 