### Chocolate

There are three tables in a room with blocks of chocolate on each. Where would be the best place for each child in the class to sit if they came in one at a time?

### Pebbles

Place four pebbles on the sand in the form of a square. Keep adding as few pebbles as necessary to double the area. How many extra pebbles are added each time?

### I'm Eight

Find a great variety of ways of asking questions which make 8.

##### Stage: 3 Short Challenge Level:

Find the number:

it's less than $100$;
it's one more than a multiple of $3$;
exactly one of the digits is prime;
if you reverse its digits, you get a prime;
it has exactly four factors;
the sum of its digits is prime;
if you multiply it by $5$, the answer is greater than $100$.

If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.

This problem is taken from the UKMT Mathematical Challenges.

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