You may also like

problem icon

Consecutive Numbers

An investigation involving adding and subtracting sets of consecutive numbers. Lots to find out, lots to explore.

problem icon

Calendar Capers

Choose any three by three square of dates on a calendar page...

problem icon

Days and Dates

Investigate how you can work out what day of the week your birthday will be on next year, and the year after...

Equal Means

Stage: 3 Short Challenge Level: Challenge Level:2 Challenge Level:2

What value of $x$ makes the mean of the first three numbers in this list equal to the mean of the last four?$$15\qquad 5 \qquad x \qquad 7 \qquad 9 \qquad 17 \qquad$$

If you liked this problem, here is an NRICH task that challenges you to use similar mathematical ideas.