100 plants each, were planted in 100 schools during Van Mahotsava. After one month, the no. of plants that survived were
recorded as in data below:

no. of plant survived less than 25 26-50 51-60 61-70 more than 70
no. of school 15 20 30 30 5
When a school is selected of random for inspection what is the probability of (i) more than 25 plants survived in school?

Answer :

We have data of 100 plants and 100 schools , As:
 

Number of plants survived	Less than 25	26 - 50	51 - 60	61 - 70	More than 70
Number of school	15	20	30	30	5

We know

Probability P ( E ) = $\frac{Total number of desired events n (\hspace{0.17em}E )}{Total number of events n (\hspace{0.17em}S\hspace{0.17em})}$

So,

When a school is selected of random for inspection , So total number of school have more than 25 plants survived   n ( E ) =  20 + 30 + 30 + 5  =  85 

And

Total number of school  n ( S ) =  100

So ,

Probability of  picking a school at random that have  more than 25 plants survived   = $\frac{85}{100} = \frac{\mathbf{17}}{\mathbf{20}}$                                                     ( Ans )