tmua.me Medium Set E Paper 1 · Question 13

A histogram represents waiting times $t$ , in minutes. Its classes and frequency densities are shown below.

\begin{array}{c|ccc} \text{Waiting time} & 0\leq t<4 & 4\leq t<12 & 12\leq t<24\\[3pt] \hline \text{Frequency density} & 2 & 1 & 1 \end{array}

The lower and upper quartiles are estimated by linear interpolation at one-quarter and three-quarters of the total frequency, respectively.

What is the estimated interquartile range, in minutes?

\dfrac{27}{4}

10

\dfrac{27}{2}

16

17

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