CBSE Class 10-Mathematics: Chapter –15 Probability Part 9
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Question 5:
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?
Answer:
Total number of marbles in the box
Total number of elementary events
(i) There are red marbles in the box.
Favourable number of elementary events
P(getting a red marble)
(ii) There are 8 white marbles in the box.
(iii) There are marbles in the box, which are not green.
Favourable number of elementary events
P (not getting a green marble)
Question 6:
A piggy bank contains hundred coins, fifty Re. 1 coins, twenty Rs. 2coins and ten Rs. 5 coins. If it is equally likely that of the coins will fall out when the bank is turned upside down, what is the probability that the coin:
(i) will be a coin?
(ii) will not be a Rs.5 coin?
Answer:
Total number of coins in a piggy bank
Total number of elementary events
(i) There are one hundred 50 coins in the piggy bank.
Favourable number of elementary events
(ii) There are coins other than Rs. 5 coin.
Favourable number of elementary events
P (falling out of a coin other than Rs. 5 coin)
Question 7:
Gopi buys a fish from a shop for his aquarium. The shopkeeper takes out one fish at random from a tank containing 5 male fishes and 8 female fishes (see figure). What is the probability that the fish taken out is a male fish?
Gopi Buys a Fish from a Shop for His Aquarium
Answer:
Total number of fish in the tank
Total number of elementary events
There are 5 male fishes in the tank.
Favourable number of elementary events
Hence, P(taking out a male fish)
Question 8:
Five cards – then ten, jack, queen, king and ace of diamonds, are well-shuffled with their face downwards. One card is then picked up at random.
(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?
Answer:
Total number of favourable outcomes = 5
(i) There is only one queen.
Favourable outcome
Hence, P (the queen)
(ii) In this situation, total number of favourable outcomes
(a) Favourable outcome
Hence,
(b) There is no card as queen.
Favourable outcome
Hence, P (the queen)