This week’s question is a simple one, although it might require a little bit of research.

What percentage of the Earth’s surface is covered by water?

Send us your answer (to the nearest whole number) to be in the running for a fab prize pack from Mad About Science, including: a salt water fuel cell car or a salt water spider bot (please tell us which one you’d like in your entry), a pack of growing beads  – just add water and watch them grow, and a pack of super water absorber  – otherwise known as ‘nappy powder’.

Email entries to, or send them via snail mail to Competitions, Mad About Science, 1A/981 Mountain Hwy, Boronia, Vic, 3135. Include your full name, age, email and postal address.  Entries must be received by Friday March 16, 2018. Click here for a full list of competition terms and conditions.