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?
Choose any four consecutive even numbers. Multiply the two middle
numbers together. Multiply the first and last numbers. Now subtract
your second answer from the first. Try it with your own numbers.
Why is the answer always 8?
Adding All Nine
Stage: 3 Challenge Level:
Remember to check your adding.
See how many $2$-digit numbers you can find that are divisible by
What happens if you just use the numbers from $1$ to $8$?
The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the
NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to
embed rich mathematical tasks into everyday classroom practice. More information on many of our other activities
can be found here.