Number Patterns Help!

[lilyrose]

I'm constantly getting confused with which term i should use
eg, in a question it'll ask for the 8th term but in the answers it'll give me the 9th term's answer.
and questions like after how many years... am i meant to use the year that that number falls under or the year after, when it has already exceeded that number
sorry if i don't make sense

your help will be greatly appreciated!!!!!

and does anyone else get that problem or am i like mentally retarded :idiot2:

[stonecold]

I was having the same issue, it because textbooks are retarted.

If you are given a starting term - t0 (i.e. before anything has happened) use:

Arithmetic: tn = a +dn              Geometric: tn=ar^n

If you are given the first term - t1 (i.e. after the first month or year or whatever) use

Arithmetic: tn= a+(n-1)d        Geometric: tn=ar^(n-1)

This should solve your problems

[krzysiek]

Cheers for that, should come in useful for me also!

Karma your way

[TyErd]

thnx!

[stonecold]

yeah, basically all of the formulas in your textbooks are for the first term and not the starting term.
if you are given a starting term t0, you have to find t1, then put that into the formula.
this way all your answers will be in line with your term numbers, and there won't be any silly mistakes and no need to punch the wall