Hi all, just joined and introduced myself in the lobby.

I have two questions which I have not been able to do the workings out for. I understand the formula to calculate arithmetic series, but I am stumped on these - hope you can help.

1. The sum of an arithmetic series is 270. The common difference is 1 and the first term is 4. Calculate the number of terms in the series.

2. The first term of an arithmetic series is 16. The 30th term is 100. Calculate S30.

Can anybody show me the process they would go through?

Thanks

Parad80.