Question

80 bulbs are selected at random from a lot and their lifetime (in hours) is recorded in the form of a frequency table given below:

$\begin{array}{cccccc}\text{Lifetime (in hours)}& 300& 500& 700& 900& 1100\\ \text{Frequency}& 10& 12& 23& 25& 10\end{array}$

One bulb is selected at random from the lot. The probability that its lifetime is 1150 hours is:

• A. $\frac{1}{80}$
• B. $\frac{7}{16}$
• C. 0
• D. 1

Answer 1

The correct option is C 0

Number of bulbs in the lot, n(S) = 80
Number of bulbs whose lifetime is 1150 hours, n(E) = 0
$\therefore$ Probability that its lifetime is 1150 hours $=\frac{n\left(E\right)}{n\left(S\right)}=\frac{0}{80}=0$.
Hence, the probability that its lifetime is 1150 hours is 0.