Nowadays the calculator is very familiar to many of us. What did
people do to save time working out more difficult problems before
the calculator existed?
This problem challenges you to find out how many odd numbers there
are between pairs of numbers. Can you find a pair of numbers that
has four odds between them?
In this investigation we are going to count the number of 1s, 2s,
3s etc in numbers. Can you predict what will happen?