## Out Of This World

By Ariel Marcy, 29 June 2023

**Difficulty: Fun**

Mariana the astronaut weighs 51 kilograms on Earth and 8.5 kilograms on the Moon. Mariana is training Javier to go to the Moon. If he weighs 78 kilograms on Earth, how much will he weigh on the Moon?

**Scroll down or click for a hint, or the answer!**

## Brainteaser hint

What’s the ratio between Earth and Moon weights? You can use a fraction or a percentage.

## Brainteaser answer

Javier will weigh 13 kilograms on the Moon.

The ratio between Earth weight and Moon weight will stay the same. Find this ratio using Mariana’s stats:

8.5 ÷ 51 = 1/6 or 16.7%

The Moon’s gravity, at the surface, is only one sixth of what we feel here on Earth!

To find Javier’s Moon weight, we can multiply his Earth weight by the ratio:

78 x 1/6 = 13 kilograms

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7 July, 2023 at 12:20 pm

kg is a mass unit and is the same on Earth as the Moon.

The force, as exerted by gravity, will be different (ie Newtons).

7 July, 2023 at 1:42 pm

Very poor explanation of the solution. Should NEVER use ‘simply’ in explaining a maths or computing or any other problem. Of course it is simple to the writer, but not necessarily to everyone else. Not a good way to encourage kids into STEM who already feel daunted by elements of it.