# Ex.15.1 Q10 Probability Solution - NCERT Maths Class 10

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## Question

A piggy bank contains hundred $$50$$$$\rm{p}$$ coins, fifty $$\rm{Re}$$ $$1$$ coins, twenty $$\rm{Rs}$$ $$2$$ coins and ten $$\rm{Rs}$$ $$5$$ coins. If it is equally likely that one of the coins will fall out when the bank is turned upside down, what is the probability that the coin

(i) will be a $$50$$$$\rm{p}$$ coin?

(ii) will not be a $$\rm{Rs}$$ $$5$$ coin?

## Text Solution

What is known?

A piggy bank contains hundred $$50$$ $$\rm{p}$$  coins, fifty $$\rm{Re}$$ $$1$$ coins, twenty $$\rm{Rs}$$ $$2$$ coins and ten $$\rm{Rs}$$ $$5$$ coins. It is equally likely that one of the coins will fall out when the bank is turned upside down.

What is unknown?

The probability that the coin

(i) will be a $$50$$$$\rm{p}$$ coin?

(ii) will not be a $$\rm{Rs}$$ $$5$$  coin?

Reasoning:

This question can be solved easily;

Find out the probability of getting $$50$$$$\rm{p}$$ coin, $$\rm{Re}$$ $$1$$ coin and $$\rm{Rs}$$ $$2$$ coin by using the formula

Probability of an event \begin{align}=\frac{\text{Number of possible outcomes}}{\text{Total no of favourable outcomes}}\end{align}

Steps:

We can use same approach as we used in question no 9.

Total no of coins$$=100+50+20+10=180$$

No of $$50$$ $$\rm{p}$$ $$=100$$
No of $$1$$ $$\rm{Re}$$ coins $$=50$$
No of $$2$$ $$\rm{Rs}$$ coins $$=20$$
No of $$5$$ $$\rm{Rs}$$ coins$$=10$$

(i) Probability of drawing $$50$$$$\rm{p}$$ coin \begin{align}=\frac{100}{180}\end{align}

(ii) Probability of getting a $$\rm{Rs}$$ $$5$$ coin \begin{align}=\frac{10}{180}=\frac{1}{18}\end{align}

Probability of not getting a $$\rm{Rs}$$ $$5$$ coin \begin{align}=1-\frac{1}{18}=\frac{17}{18}\end{align}

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