This Sudoku requires you to do some working backwards before working forwards.
Got It game for an adult and child. How can you play so that you know you will always win?
If you take a three by three square on a 1-10 addition square and multiply the diagonally opposite numbers together, what is the difference between these products. Why?
A cinema has 100 seats. Show how it is possible to sell exactly 100 tickets and take exactly Â£100 if the prices are Â£10 for adults, 50p for pensioners and 10p for children.
Can you find six numbers to go in the Daisy from which you can make all the numbers from 1 to a number bigger than 25?
By selecting digits for an addition grid, what targets can you make?
Different combinations of the weights available allow you to make different totals. Which totals can you make?
The letters in the following addition sum represent the digits 1 ... 9. If A=3 and D=2, what number is represented by "CAYLEY"?
Find the values of the nine letters in the sum: FOOT + BALL = GAME
How many different differences can you make?
This Sudoku, based on differences. Using the one clue number can you find the solution?
Use the differences to find the solution to this Sudoku.
Can you explain the strategy for winning this game with any target?
Make your own double-sided magic square. But can you complete both sides once you've made the pieces?
How many solutions can you find to this sum? Each of the different letters stands for a different number.
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. . . .
Choose two digits and arrange them to make two double-digit numbers. Now add your double-digit numbers. Now add your single digit numbers. Divide your double-digit answer by your single-digit answer. . . .
This article explains how to make your own magic square to mark a special occasion with the special date of your choice on the top line.
Crosses can be drawn on number grids of various sizes. What do you notice when you add opposite ends?
In the following sum the letters A, B, C, D, E and F stand for six distinct digits. Find all the ways of replacing the letters with digits so that the arithmetic is correct.
Do you notice anything about the solutions when you add and/or subtract consecutive negative numbers?
Replace each letter with a digit to make this addition correct.
Delight your friends with this cunning trick! Can you explain how it works?
Investigate the different ways that fifteen schools could have given money in a charity fundraiser.
Find out about Magic Squares in this article written for students. Why are they magic?!
There are exactly 3 ways to add 4 odd numbers to get 10. Find all the ways of adding 8 odd numbers to get 20. To be sure of getting all the solutions you will need to be systematic. What about. . . .
Five numbers added together in pairs produce: 0, 2, 4, 4, 6, 8, 9, 11, 13, 15 What are the five numbers?
The country Sixtania prints postage stamps with only three values 6 lucres, 10 lucres and 15 lucres (where the currency is in lucres).Which values cannot be made up with combinations of these postage. . . .
Ann thought of 5 numbers and told Bob all the sums that could be made by adding the numbers in pairs. The list of sums is 6, 7, 8, 8, 9, 9, 10,10, 11, 12. Help Bob to find out which numbers Ann was. . . .
Here is a chance to play a version of the classic Countdown Game.
How many ways can you find to put in operation signs (+ - x Ã·) to make 100?
Try entering different sets of numbers in the number pyramids. How does the total at the top change?
Can you explain how this card trick works?
What is the sum of all the digits in all the integers from one to one million?
Here is a chance to play a fractions version of the classic Countdown Game.
In this 100 square, look at the green square which contains the numbers 2, 3, 12 and 13. What is the sum of the numbers that are diagonally opposite each other? What do you notice?
There are nasty versions of this dice game but we'll start with the nice ones...
A combination mechanism for a safe comprises thirty-two tumblers numbered from one to thirty-two in such a way that the numbers in each wheel total 132... Could you open the safe?
Using the 8 dominoes make a square where each of the columns and rows adds up to 8
This article gives you a few ideas for understanding the Got It! game and how you might find a winning strategy.
Some Games That May Be Nice or Nasty for an adult and child. Use your knowledge of place value to beat your opponent.
How is it possible to predict the card?
An investigation involving adding and subtracting sets of consecutive numbers. Lots to find out, lots to explore.
Try out some calculations. Are you surprised by the results?
When I type a sequence of letters my calculator gives the product of all the numbers in the corresponding memories. What numbers should I store so that when I type 'ONE' it returns 1, and when I type. . . .
This addition sum uses all ten digits 0, 1, 2...9 exactly once. Find the sum and show that the one you give is the only possibility.
Three children are going to buy some plants for their birthdays. They will plant them within circular paths. How could they do this?
What is the largest number you can make using the three digits 2, 3 and 4 in any way you like, using any operations you like? You can only use each digit once.
Skippy and Anna are locked in a room in a large castle. The key to that room, and all the other rooms, is a number. The numbers are locked away in a problem. Can you help them to get out?
What happens when you add a three digit number to its reverse?