Question

A factory manufacturing car batteries made a survey in the field on the life of these batteries. The data obtained was as follows:

$\begin{array}{cccccc}\text{Life Time (in months)}& \text{Less than 24}& 24-36& 36-48& \text{more than 48}& \text{Total Batteries}\\ \text{Number of batteries}& 50& 240& 550& 160& 1000\end{array}$

What is the probability that a battery chosen at random

(i) will not last more than 36 months?

(ii) will last for four years? [2 MARKS]

Answer 1

Solution: [1.5 Marks for each section]

i) Number of batteries that wont last for more than 36 months = 50 + 240 = 290
Probability that the battery will not last more than 36 months
$=\frac{290}{1000}=0.29$

ii) Number of batteries that lasted 4 years = 160
Probability that a battery will last 4 years
$=\frac{160}{1000}=0.16$