### 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...

### Summing Consecutive Numbers

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

### Always the Same

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?

# Lower Bound

##### Age 11 to 14 Challenge Level:

Investigate the following sequence of fraction sums:
\begin{eqnarray} \frac{1}{2} &+& \frac{2}{1} = \\ \frac{2}{3} &+& \frac{3}{2} = \\ \frac{3}{4} &+& \frac{4}{3} = \\ \frac{4}{5} &+& \frac{5}{4} = \end{eqnarray}
What would you get if you continued this sequence for ever?

What do you think will happen if you add the squares of these fractions, that is:
\begin{eqnarray} \left(\frac{1}{2}\right)^2 &+& \left(\frac{2}{1}\right)^2 = \\ \left(\frac{2}{3}\right)^2 &+& \left(\frac{3}{2}\right)^2 = \end{eqnarray}
and so on?