Place value

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.
problem
Back to basics

Age

14 to 16

Challenge level

Find b where 3723(base 10) = 123(base b).
problem
Number rules - OK

Age

14 to 16

Challenge level

Can you produce convincing arguments that a selection of statements about numbers are true?
problem
X marks the spot

Age

11 to 14

Challenge level

When the number x 1 x x x is multiplied by 417 this gives the answer 9 x x x 0 5 7. Find the missing digits, each of which is represented by an "x" .
problem
Really Mr. Bond

Age

14 to 16

Challenge level

115^2 = (110 x 120) + 25, that is 13225 895^2 = (890 x 900) + 25, that is 801025 Can you explain what is happening and generalise?
problem
eNRICHing experience

Age

14 to 16

Challenge level

Find the five distinct digits N, R, I, C and H in the following nomogram