### Number Round Up

Arrange the numbers 1 to 6 in each set of circles below. The sum of each side of the triangle should equal the number in its centre.

### Numbers as Shapes

Use cubes to continue making the numbers from 7 to 20. Are they sticks, rectangles or squares?

### How Odd

This problem challenges you to find out how many odd numbers there are between pairs of numbers. Can you find a pair of numbers that has four odds between them?

# Largest Even

##### Stage: 1 Challenge Level:

I have a pile of nine digit cards numbered $1$ to $9$.

I take one of the cards.  It is the $3$.

Which card would you choose so you could make the largest possible two-digit even number with the two cards?

We put the cards back in the pile.  This time, I choose the $6$. Which card would you choose this time to make the largest possible two-digit even number?

Have a go at this with a partner.  One of you chooses the first digit from the set of cards.  The second person then chooses a card to make the largest possible two-digit even number. You can then swap over.

Try it several times so you are sure you have a good method. Talk about your ideas with your partner so you agree together on a 'best' method.

How would your strategy change if you had to make the largest two-digit odd number?

If you don't have a partner to work with, you could use the interactivity below.  The computer selects one digit at random.   You must then choose a digit to make the largest possible two-digit even number or largest possible two-digit odd number.

Enter the biggest two-digit number you can think of that uses the digit:

The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice. More information on many of our other activities can be found here.
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