# 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.

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

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.

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?

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?