Crosses can be drawn on number grids of various sizes. What do you notice when you add opposite ends?
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.
My two digit number is special because adding the sum of its digits to the product of its digits gives me my original number. What could my number be?
Arrange the numbers 1 to 16 into a 4 by 4 array. Choose a number. Cross out the numbers on the same row and column. Repeat this process. Add up you four numbers. Why do they always add up to 34?
Robert noticed some interesting patterns when he highlighted square numbers in a spreadsheet. Can you prove that the patterns will continue?
32 x 38 = 30 x 40 + 2 x 8; 34 x 36 = 30 x 40 + 4 x 6; 56 x 54 = 50 x 60 + 6 x 4; 73 x 77 = 70 x 80 + 3 x 7 Verify and generalise if possible.
Jo has three numbers which she adds together in pairs. When she does this she has three different totals: 11, 17 and 22 What are the three numbers Jo had to start with?”
Think of a number and follow my instructions. Tell me your answer, and I'll tell you what you started with! Can you explain how I know?
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. . . .
Choose four consecutive whole numbers. Multiply the first and last numbers together. Multiply the middle pair together. What do you notice?
Pick the number of times a week that you eat chocolate. This number must be more than one but less than ten. Multiply this number by 2. Add 5 (for Sunday). Multiply by 50... Can you explain why it. . . .
How many more miles must the car travel before the numbers on the milometer and the trip meter contain the same digits in the same order?
Make some loops out of regular hexagons. What rules can you discover?
Find b where 3723(base 10) = 123(base b).
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 job needs three men but in fact six people do it. When it is finished they are all paid the same. How much was paid in total, and much does each man get if the money is shared as Fred suggests?
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. . . .
Can you explain how this card trick works?
First of all, pick the number of times a week that you would like to eat chocolate. Multiply this number by 2...
Create some shapes by combining two or more rectangles. What can you say about the areas and perimeters of the shapes you can make?
The Number Jumbler can always work out your chosen symbol. Can you work out how?
15 = 7 + 8 and 10 = 1 + 2 + 3 + 4. Can you say which numbers can be expressed as the sum of two or more consecutive integers?
Think of two whole numbers under 10, and follow the steps. I can work out both your numbers very quickly. How?
Think of a number, add one, double it, take away 3, add the number you first thought of, add 7, divide by 3 and take away the number you first thought of. You should now be left with 2. How do I. . . .
The squares of any 8 consecutive numbers can be arranged into two sets of four numbers with the same sum. True of false?
Use the numbers in the box below to make the base of a top-heavy pyramid whose top number is 200.
Try entering different sets of numbers in the number pyramids. How does the total at the top change?
Think of a number and follow the machine's instructions... I know what your number is! Can you explain how I know?
How to build your own magic squares.
A task which depends on members of the group noticing the needs of others and responding.
Think of a two digit number, reverse the digits, and add the numbers together. Something special happens...
Choose any four consecutive even numbers. Multiply the two middle numbers together. Multiply the first and last numbers. Now subtract your second answer from the first. Try it with your own. . . .
Account of an investigation which starts from the area of an annulus and leads to the formula for the difference of two squares.
Think of a number Multiply it by 3 Add 6 Take away your start number Divide by 2 Take away your number. (You have finished with 3!) HOW DOES THIS WORK?
Find some triples of whole numbers a, b and c such that a^2 + b^2 + c^2 is a multiple of 4. Is it necessarily the case that a, b and c must all be even? If so, can you explain why?
Many numbers can be expressed as the difference of two perfect squares. What do you notice about the numbers you CANNOT make?
List any 3 numbers. It is always possible to find a subset of adjacent numbers that add up to a multiple of 3. Can you explain why and prove it?
I added together the first 'n' positive integers and found that my answer was a 3 digit number in which all the digits were the same...
A little bit of algebra explains this 'magic'. Ask a friend to pick 3 consecutive numbers and to tell you a multiple of 3. Then ask them to add the four numbers and multiply by 67, and to tell you. . . .
If a sum invested gains 10% each year how long before it has doubled its value?
A box has faces with areas 3, 12 and 25 square centimetres. What is the volume of the box?
Janine noticed, while studying some cube numbers, that if you take three consecutive whole numbers and multiply them together and then add the middle number of the three, you get the middle number. . . .
Let S1 = 1 , S2 = 2 + 3, S3 = 4 + 5 + 6 ,........ Calculate S17.
Attach weights of 1, 2, 4, and 8 units to the four attachment points on the bar. Move the bar from side to side until you find a balance point. Is it possible to predict that position?
What is the total number of squares that can be made on a 5 by 5 geoboard?
Brian swims at twice the speed that a river is flowing, downstream from one moored boat to another and back again, taking 12 minutes altogether. How long would it have taken him in still water?
The sum of the numbers 4 and 1 [1/3] is the same as the product of 4 and 1 [1/3]; that is to say 4 + 1 [1/3] = 4 × 1 [1/3]. What other numbers have the sum equal to the product and can this be so for. . . .
Can you find rectangles where the value of the area is the same as the value of the perimeter?
The number 27 is special because it is three times the sum of its digits 27 = 3 (2 + 7). Find some two digit numbers that are SEVEN times the sum of their digits (seven-up numbers)?
If a two digit number has its digits reversed and the smaller of the two numbers is subtracted from the larger, prove the difference can never be prime.