# Proof for All (st)ages

Creating convincing arguments or "proofs" to show that statements are always true is a key mathematical skill.

The problems in this feature offer students the chance to identify number patterns, make conjectures and create convincing mathematical proofs.

Many of the problems in this feature include proof sorting activities which challenge students to rearrange statements in order to recreate clear, rigorous proofs.  These tasks aim to introduce students to the formality and logic of mathematical proof.

You can watch a recording of the webinar in which we discussed the mathematical thinking which can be prompted by these activities.

The last day for students to send in their solutions to the live problems is Monday 31 January.

Plus magazine has a selection of interesting articles about proofs here

### Three Neighbours

##### Age 7 to 14Challenge Level
Take three consecutive numbers and add them together. What do you notice?

### Three Consecutive Odd Numbers

##### Age 11 to 16Challenge Level
How many sets of three consecutive odd numbers can you find, in which all three numbers are prime?

##### Age 11 to 16Challenge Level
Is there a quick and easy way to calculate the sum of the first 100 odd numbers?

### Where Are the Primes?

##### Age 11 to 16Challenge Level
What can we say about all the primes which are greater than 3?

### What Does it All Add up To?

##### Age 11 to 18Challenge Level
If you take four consecutive numbers and add them together, the answer will always be even. What else do you notice?

### Different Products

##### Age 14 to 16Challenge Level
Take four consecutive whole numbers. Multiply the first and last numbers together. Multiply the middle pair together. What do you notice?

### Difference of Odd Squares

##### Age 14 to 18Challenge Level
$40$ can be written as $7^2 - 3^2.$ Which other numbers can be written as the difference of squares of odd numbers?

### Impossible Sums

##### Age 14 to 18Challenge Level
Which numbers cannot be written as the sum of two or more consecutive numbers?

### Adding Odd Numbers (part 2)

##### Age 16 to 18Challenge Level
Can you use Proof by Induction to establish what will happen when you add more and more odd numbers?

### Direct Logic

##### Age 16 to 18Challenge Level
Can you work through these direct proofs, using our interactive proof sorters?

### KS5 Proof Shorts

##### Age 16 to 18Challenge Level
Here are a few questions taken from the Test of Mathematics for University Admission (or TMUA).

### Dodgy Proofs

##### Age 16 to 18Challenge Level
These proofs are wrong. Can you see why?

We are very grateful to the Heilbronn Institute for Mathematical Research for their generous support for the development of these resources.