A little problem concerning maths?

Question

My son has asked me a maths question, and i am no maths genius.

It is a missing number problem, and this is it as follows;

1 2 ??? 15 52.5 210 945

If anyone could help, i am quite an idiot at maths.

Thanks,

Answer 1

ok so if u divide the last couple of numbers you will find that the diviser goes up by .5 for each term. So multiply 2 by 2.5 and then that answer by three and you wil get the pattern. The missing number is 5