# CBSE Class 10-Mathematics: Chapter –15 Probability Part 11

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**Question 14:**

A bag contains 5 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 there be blue balls in the bag.

Total number of balls in the bag

Now, Probability of drawing a blue ball

And Probability of drawing a blue ball

But according to question,

Hence, there are blue balls in the bag.

**Question 15:**

A box contains balls out of which are black. If one ball is drawn at random from the box, what is the probability that it will be a black ball?

If 6 more black balls are put in the box, the probability of drawing a black ball is now double of what it was before. Find

**Answer:**

There are balls in the box.

Therefore, total number of favourbale outcomes

The number of favourable outcomes

Therefore, (getting a black ball)

If 6 more balls put in the box, then

Total number of favourable outcomes

And Number of favourable outcomes

According to question,

**Question 16:**

A jar contains 24 marbles, some are green and others are blue. If a marble is drawn at random from the jar, the probability that it is green is . Find the number if blue balls in the jar.

**Answer:**

Here, Total number of favourable outcomes

Let there be green marbles.

Therefore, Favourable number of outcomes

But

Therefore, number of green marbles are

And number of blue marbles

**Question 17:**

Why is tossing a coin considered is the way of deciding which team should get the ball at the beginning of a football match?

**Answer:**

Probability of head

Probability of tail

i.e.

Probability of getting head and tail both are same.

Tossing a coin considered tobe fair way.

**Question 18:**

An unbiased die is thrown, what is the probability of getting an even number?

**Answer:**

Total number of outcomes are , which are 6 in number favourable

Required probability