Many numbers can be expressed as the sum of two or more consecutive integers. For example, 15=7+8 and 10=1+2+3+4. Can you say which numbers can be expressed in this way?

Arrange the numbers 1 to 16 into a 4 by 4 array. Choose a number.
Cross out the numbers on the same row and column. Repeat this
process. Add up you four numbers. Why do they always add up to 34?

Refuelling

Stage: 3 Short Challenge Level:

It takes $\frac{s}{r}$ gallons to travel $1$ mile, so it takes
$$\frac{s}{r}\times t= \frac{st}{r} \; \text{gallons}$$
to travel $t$ miles