### Double Digit

Choose two digits and arrange them to make two double-digit numbers. Now add your double-digit numbers. Now add your single digit numbers. Divide your double-digit answer by your single-digit answer. Try lots of examples. What happens? Can you explain it?

### Pyramids

What are the missing numbers in the pyramids?

The square numbers around $1871$ are $42^2=1764$, $43^2=1849$ and $44^2=1936$. The only realistic possibility is that de Morgan was $43$ in the year $1849$, which puts his date of birth at $1806$.