** T****h****e Main Challenge**

All nine numbers from **21 to 29 inclusive** must be allocated to a letter below so that each allocated number satisfies the condition given on the line:

- (a) even number,
- (b) factor of 144,
- (c) power of 3,
- (d) prime number,
- (e) digits which differ by 1,
- (f) exactly 3 factors,
- (g) multiple of 7,
- (h) equal to the sum of all its factors (except the number itself),
- (i) 2nd digit is greater than its 1st digit.

But, the numbers **21 to 29** should only appear once each above!

**The 7puzzle Challenge**

The playing board of **the 7puzzle game** is a 7-by-7 grid containing 49 different numbers, ranging from **2 **up to **84**.

The 1st & 7th rows contain the following fourteen numbers:

2 4 9 11 14 15 22 24 27 30 40 70 72 77

Which odd number, when 21 is added to it, becomes a square number?

**The Lagrange Challenge**

*Lagrange’s Four-Square Theorem* states that every positive integer can be made by adding up to four square numbers.

For example, **7** can be made by **2²+1²+1²+1²** (or 4+1+1+1).

There are THREE ways of making **18 **when using *Lagrange’s Theorem*. Can you find them?

**The Mathematically Possible Challenge**

Using **5**, **6** and **8 **once each, with + – × ÷ available, which are the only TWO numbers it is possible to make from the list below?

9 18 27 36 45 54 63 72 81 90

#*9TimesTable*

**The Target Challenge**

Can you arrive at **18** by inserting **2**, **3**, **4** and **6** into the gaps on each line?

- ◯×◯–◯×◯ = 18
- ◯÷◯×◯×◯² = 18
- (◯÷◯)³×√◯÷◯ = 18

**A****nswers **can be found **here**.

**Click Paul Godding for details of online maths tuition.**