Why do this
problem?
This
activity
appeals to many pupils much more than being presented with "sums"
to do. It may make use of number bonds and facts that the pupils
already know.
Possible approach
Use something fairly large to represent the $24$ carriages -
even carriages from a toy train set would be great! You could
create an IWB file that allowed you to create multiple copies of
the carriage and to move them around the screen.
Encourage children to suggest some ways of making the trains
to start with and display them using whatever you have chosen.
If possible, keep these to be referred to later.
Give children time to work in pairs on the challenge.
You may want them to put each solution on a separate
strip of paper, because then you could use these in the plenary to
order the solutions in some way and this will help the group work
out if they have missed any out.
Key questions
How many carriages here?
Which train has most carriages?
How many carriages have you used?
Possible extension
Explore the results for $20, 21 22$ and $23$ carriages, and
compare them.
Encourage children to ask "I wonder what would happenn if
...?".
Possible support
Some of the youngest pupils may need help in counting
accurately and not counting the same carriages twice.