We received many correct answers to this problem - thank you! Most of you had done it a similar way, by drawing a table.

Joanne and Liam from Moorfield Junior School explained their approach very clearly:

We each worked on a different plant and each time we worked out the height for that day we checked to see if we had the same answer until we did. This is what it looked like.......

The answer is six days and the plant would be 63cm tall