Multiplication and division

problem

Code Breaker

Age

7 to 11

Challenge level

2 out of 3

This problem is based on a code using two different prime numbers less than 10. You'll need to multiply them together and shift the alphabet forwards by the result. Can you decipher the code?
problem

Slippy Numbers

Age

11 to 14

Challenge level

3 out of 3

The number 10112359550561797752808988764044943820224719 is called a 'slippy number' because, when the last digit 9 is moved to the front, the new number produced is the slippy number multiplied by 9.
problem

Eminit

Age

11 to 14

Challenge level

3 out of 3

The number 8888...88M9999...99 is divisible by 7 and it starts with the digit 8 repeated 50 times and ends with the digit 9 repeated 50 times. What is the value of the digit M?
problem

X Marks the Spot

Age

11 to 14

Challenge level

3 out of 3

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

A One in Seven Chance

Age

11 to 14

Challenge level

3 out of 3

What is the remainder when 2^{164}is divided by 7?
game

Shut the Box for Two

Age

5 to 7

Challenge level

1 out of 3

Shut the Box game for an adult and child. Can you turn over the cards which match the numbers on the dice?
problem

Starfish Spotting

Age

5 to 7

Challenge level

2 out of 3

How many starfish could there be on the beach, and how many children, if I can see 28 arms?
problem

What's Left?

Age

5 to 7

Challenge level

2 out of 3

Use this grid to shade the numbers in the way described. Which numbers do you have left? Do you know what they are called?
problem

Twizzle's Journey

Age

5 to 7

Challenge level

3 out of 3

Twizzle, a female giraffe, needs transporting to another zoo. Which route will give the fastest journey?
problem

Mobile Numbers

Age

5 to 11

Challenge level

1 out of 3

In this investigation, you are challenged to make mobile phone numbers which are easy to remember. What happens if you make a sequence adding 2 each time?