1. 10x + y What do you notice? x = 2 and y = 1? x = 4 and y = 5?
On your whiteboards:
10x + y
What is the value of this expression when:
x = 2 and y = 1?
x = 4 and y = 5?
x = 6 and y = 6?
What do you notice?

2. 10x + y On your whiteboards:
Can every 2 digit number be represented in this way?
Why?
Write an expression on your whiteboard to represent a three digit number.

3. What do you notice about all of the values?
On your whiteboards: 2n
Choose an integer value for n
Find the value of the expression for your chosen integer
Look around the classroom
What do you notice about all of the values?

4. 5n 3n 2n + 1 On your whiteboards:
When n is an integer what kind of numbers do the following expressions represent? 5n 3n
2n + 1

5. Challenge:
When n is an integer, two consecutive integers can be represented as n, n+1.
What kind of number will the sum of two consecutive numbers be?

6. What do you notice? Always a multiple introduction video.
On your whiteboards:
Think of a two-digit number and write it down.
Reverse the digits and add your answer to your original number.
What answers did you get?
Look around the room
What do you notice?

7. What do you notice? On your whiteboards:
Think of a two-digit number and write it down.
Reverse the digits and add your answer to your original number.
What answers did you get?
Look around the room
What do you notice?

8. In your pairs:
Without trying all possible two-digit numbers, try to find a convincing explanation why it will always work.

9. Alison’s explanation
Charlie’s explanation

10. Choose one of the problems below to investigate.
In your pairs:
Choose one of the problems below to investigate.
Take any two-digit number.
Reverse the digits, and subtract your answer
from your original number.
What do you notice?
Add its digits, and subtract your answer from
your original number.
Take any three-digit number.
Take any five-digit number.