You may also like

problem icon

Calendar Capers

Choose any three by three square of dates on a calendar page...

problem icon

Adding All Nine

Make a set of numbers that use all the digits from 1 to 9, once and once only. Add them up. The result is divisible by 9. Add each of the digits in the new number. What is their sum? Now try some other possibilities for yourself!

problem icon

Picture Story

Can you see how this picture illustrates the formula for the sum of the first six cube numbers?


Stage: 3 Challenge Level: Challenge Level:1
There are 30 students in a class and it is found that in any subset of 4 students from the class each student has exchanged Christmas cards with the other three. Show that some students have exchanged cards with all the other students in the class. How many such students are there?