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# Ex.15.1 Q9 Probability Solution - NCERT Maths Class 9

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## Question

Eleven bags of wheat flour, each marked $$5\,\rm kg$$, actually contained the following weights of flour (in kg)

$$4.97, 5.05, 5.08, 5.03,\\ 5.00, 5.06, 5.08,\\ 4.98, 5.04, 5.07, 5.00$$

Find the probability that any of these bags chosen at random contains more than $$5 \,\rm kg$$ of flour.

Video Solution
Probability
Ex exercise-15-1 | Question 9

## Text Solution

What is known?

No of bags of specific weights.

What is unknown?

Probability of any of the bags containing more than $$5\,\rm kg$$ of flour.

Reasoning:

The empirical probability $$P(E)$$ of an event $$E$$ happening, is given by:

\begin{align}{P}({E})=\frac{ \begin{pmatrix} \text { Number of trials in which }\\ \text{the event happened } \end{pmatrix} }{ \text { The total number of trials } }\end{align}

Use probability to derive the solution where

Probability $$P$$ Weight of the bag

\begin{align}=\frac{ \begin{pmatrix} \text { Number of bags} \\ \text{ of specific weight } \end{pmatrix} }{\text { Total number of bags }}\end{align}

Steps:

Total no of bags $$= 11$$

No of bags more than $$5\,\rm kg$$ of flour $$= 7$$

Probability (Bag weighing more than $$5\,\rm kg$$ of flour )

\begin{align}\\&=\frac{ \begin{pmatrix} \text { Number of bags weighing} \\ \text{ more than 5 kg of flour } \end{pmatrix}} {\text { Total number of bags }} \\ &=\frac{7}{11}\end{align}

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