Challenge of the Week

Monday 28th April 2025

Sequences and Arguments

A teacher gives his class the sequence 1, 2, 5, ... and asks them to work out the next number.

Alan says, "The answer is 14." Betty says, "You're wrong! I think it is 15." Carl says, "Nah, you're both wrong - I make it 26."

1) All three of their answers are valid - try to work out what they each did to reach their answer using a valid sequence.

2) Can you find three more possible sequences which give different values to the ones above? Explain your pattern for each sequence.