Challenge type: What Comes Next? · Difficulty: ★★★☆☆ Medium
Coders spot patterns so they can write loops instead of doing the same thing over and over. Try this one.
The pattern in words: 9, 12, 15, 18, 21, 24, and then… what?
Your choices
- A: 30
- B: 17
- C: 29
- D: 27
Need a hint?
Find the difference between two numbers next to each other.
Did you know? When coders spot a pattern, they can write a loop: a few lines of code that repeat the rule as many times as they like. The answer page shows this pattern as real Python code!
For teachers and grown-ups
Skills practised: Pattern recognition, abstraction, and predicting the next step of a rule.
The big idea: Spotting a pattern lets a programmer replace lots of repeated steps with one short loop.
Questions to ask:
- What is the rule, in your own words?
- How many items repeat before the pattern starts again?
- What would the 20th item be? How could you work it out without drawing them all?
Take it further: Children invent their own pattern with a hidden rule and challenge a partner to find it.