A market stall records the number of minutes that its customers spend at the stall…

Contributed by StemPy Lab

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

A market stall records the number of minutes that its customers spend at the stall. The class marks are $5, 15, 25, 35$ and $45$ minutes, and the frequencies are $6, x, 12, y$ and $8$ . Two frequencies were lost. The stall owner knows that there were $50$ customers and that the mean time was $23$ minutes.

Find $x$ and $y$ .

Show that no table of this kind can have the mean $20$ .

Need a reminder? The key ideaShow

Name the missing frequency $x$ , write the clue as a formula in $x$ , solve, and check. For the mean, use $\bar{x} = \dfrac{\sum fx}{N}$ with both $\sum fx$ and $N$ in terms of $x$ . For the median, decide the median class first. A frequency is a whole number that is not negative.

The worked solution

Have you tried it?

Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

← All Problems

← The marks of the candidates in a school test are grouped in the table below…Next →

More onStatistics and Probability › Statistics

Discussion (0)

Loading…