# CBSE Class 10-Mathematics: Chapter –15 Probability Part 2

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**Question 7:**

A bag contais red balls and some blue balls. If the probability of drawing a blue ball is double that of a red ball. Determine the number of blue balls in the bag.

**Answer:**

Let the number of blue balls is the bag be

Then total number of balls is the bag

Number of all possible outcomes

Number of outcomes favourable to the event of drawing a ball

(Q there are x blue balls)

Probability of drawing a blue ball

Similarly, probability of drawing a red ball

According to the answer

**Question 8:**

A box contains 12 balls out of which x are black. If one ball is drawn at random from the box. What is the probability that it will be a black ball? If more black balls are out in the box the probability of drawing a black ball is now double of what it was before. Find x?

**Answer:**

Number of all possible outcomes =12

Number of outcomes favourable to the event of drawing black ball

Required probability

Now when more black balls are out in the box.

Number of all possible outcomes

Number of outcomes favourable to the event of drawing a black ball

Probability of drawing a black ball

According to the question.

**Question 9:**

If of the populations have black eves. have brown eyes and the remaining have blue eyes. What is the probability that a person selected at random has (i) Blue eves (ii) Brown or black eves (iii) Blue or black eves (iv) neither blue nor brown eves

**Answer:**

No. of black eves

No. of Brown eves

No. of blue eves

Total no. of eves

i.

ii.

iii.

**Question 10:**

Find the probability of having Sundays in

i. a leap year

ii. a non leap year

**Answer:**

An ordinary year has days i.e. weeks and 1 day

Thisn day can be any one of the days of the week.

Pith at this day is Sunday

Hence. 53 Sunday

A leap year days i.e. weeks and days

This day can be any one of the days of the week

Hence,

**Question 11:**

Five cards – the ten. Jack, queen, king and ace, are well shuffied with their face downwards. One card is then nicked un at random.

i. What is the probability that the card is a queen?

ii. If the queen is drawn and out aside, what is the probability that the second card nicked up is a (a) an ace (b) a queen

**Answer:**

Here, the total number of elementary events

i. Since, there is only one queen

Favourable number of elementary events

Probability of getting an ace card

(b) Since, there is no queen (as queen is nut aside)

Favourable number of elementary events

Probability of getting an ace card