Answer and explanation for the Co-Sci qn.

Hi Sarah

the answer for the Earth and Mars qn. is 'the Earth and Mars attract',

because

'The planets are too far apart from one another for their gravitational attractions

to be very noticeable. The earth does attract Mars (and vice versa), but so

weakly that this gravitational force is nearly impossible to detect.'

I am still thinking of the 'atom 18 and 19' question. Will let you know once I have a solution for it.

There are practice papers for IGCSE math at this website: http://www.xtremepapers.com/. When we have finished going through those given by your school, we'll try the questions from this website. They also have for other subjects. You can take a look at them if you need further practice for other subjects.

Happy studying!