Place value

problem
Think of two numbers

Age

11 to 14

Challenge level

Think of two whole numbers under 10, and follow the steps. I can work out both your numbers very quickly. How?
problem
Back to the planet of Vuvv

Age

11 to 14

Challenge level

There are two forms of counting on Vuvv - Zios count in base 3 and Zepts count in base 7. Can you work out in which direction the Zios and Zepts were looking, based on the information you're given?
problem
Reach 100

Age

7 to 11

Challenge level

Choose four different digits from 1-9 and put one in each box so that the resulting four two-digit numbers add to a total of 100.
problem
All the digits

Age

7 to 11

Challenge level

This multiplication uses each of the digits 0 - 9 once and once only. Using the information given, can you replace the stars in the calculation with figures?
problem
More mathematical mysteries

Age

11 to 14

Challenge level

Write down a three-digit number Change the order of the digits to get a different number Find the difference between the two three digit numbers Follow the rest of the instructions then try to explain why this works.
problem
Spell by numbers

Age

7 to 11

Challenge level

Can you substitute numbers for the letters in these sums?
problem
Eleven

Age

11 to 14

Challenge level

Replace each letter with a digit to make this addition correct.
problem
Please explain

Age

11 to 14

Challenge level

Visitors to Earth from the distant planet of Zub-Zorna were amazed when they found out that when the digits in this multiplication were reversed, the answer was the same! Find a way to explain why this works.
problem
Read this page

Age

11 to 14

Challenge level

Replace the letters with numbers to make the addition work out correctly. R E A D + T H I S = P A G E
problem
What number?

Age

5 to 7

Challenge level

I am less than 25. My ones digit is twice my tens digit. My digits add up to an even number.