Question1. Find $n$ for arithmetic series: a) $t_1=8, t_n=68, S_n=608$ b) $t_1=-6, t_n=21, S_n=75$
2. Find $t_{10}$ and $S_{10}$ for series: a) $5+10+15+\cdots$ b) $10+7+4+\cdots$ c) $(-10)+(-14)+(-18)+\cdots$ d) $2.5+3+3.5+\cdots$
3. a) Sum of multiples of 4 between 1 and 999 b) Sum of multiples of 6 between 1 and 999