Problem
Select a number less than 20. Skip count with it to 1000. How many numbers can you find that will hit no hundreds through to 1000.

What is this problem about?
This problem explores the idea that large numbers are made up of smaller numbers. It also helps children form a more accurate idea of the value of a 1000. The children develop their understanding of multiples by skip counting with a calculator. Skip counting with a calculator is easy and intriguing. (You can use the repeat function on most calculators to skip count. For example skip count by sevens by pressing: 7 + = = = etc) The calculator allows the children to deal with a greater range of large number problems than they could approach if they had to perform all the computation with pen and paper. In this problem the calculator allows them to look for patterns in the multiples of numbers.

Achievement objectives
Number (Level 3)
- explain the meaning of digits in any whole number

Mathematical processes
- devise and use problem solving strategies

Resources required
Calculators
Blackline master of the problem (English)
Blackline master of the problem (Maaori)

Specific learning outcomes
The children will be able to:
- use calculators to explore multiples of numbers to a 1000
- identify number patterns in multiples.

1. Introduce the problem by using the calculators to skip count in 8's.
2. Record the multiples of 8 as they are found up to 200.
3. Ask the children to predict which other hundreds they think would be "hit" (multiples of 8). Give them time to find the hits (200, 400, 600, 800)
4. Discuss the pattern found.
5. Read the problem for the children to work on in pairs.
6. Visit with the pairs as they work asking:
   What are the next hundreds you will hit exactly? How do you know?
   Which number will you pick next? Will that number hit a hundreds number? Which one?
   Can you pick a number that will hit every hundred through to 1000? Are there others?
7. Encourage the children to organise their findings into a list and use the list to look for patterns.
8. Share lists and patterns.

Extension to the problem
What numbers will hit every hundred through 1000?