Mr. P’s Parent Maths Problem of the Week

Last Week’s Problem:
Six woodworms made their home in an old wooden cube made up of identical small cubes. Each one drilled a tunnel all the way through the cube, parallel to one of its edges. The diagram shows the entrances to the six tunnels. How many small cubes don’t have a tunnel drilled through them?

A)9                  B)12                  C) 15                  D) 18                  E) 21

Solution:
Last week’s problem was quite a tricky one, as it required you to “think in 3D” to work out how many cubes would not be eaten by the woodworms.

The method I found easiest was to first calculate the total number of small cubes, then work out how many cubes had been “eaten through”, and finally subtract one from the other.

There are 27 small cubes altogether. After carefully counting the cubes that were eaten through, while being mindful of overlaps, I determined that 15 cubes had been “eaten”.

So: 27 − 15 = 12

Therefore, the correct answer is B.

Problem for Week 2 Term 3

Determine the missing number at the top of the staircase.