### Number Detective

Follow the clues to find the mystery number.

### Red Even

You have 4 red and 5 blue counters. How many ways can they be placed on a 3 by 3 grid so that all the rows columns and diagonals have an even number of red counters?

### Prime Magic

Place the numbers 1, 2, 3,..., 9 one on each square of a 3 by 3 grid so that all the rows and columns add up to a prime number. How many different solutions can you find?

# Becky's Number Plumber

##### Age 7 to 11 Challenge Level:

This problem has been inspired by learners who were working on the Become Maths Detectives Project.

You may like to watch the video in the Become Maths Detective Project before having a go at this activity.

Becky created a number plumber which multiplies by $5$ and subtracts $4$.
Click on the picture to explore Becky's number plumber.

What do you notice about the units digit of the answer each time?
Can you explain why this happens?
Can you find any other numbers that work in a similar way?