Find the following
1. sum of 6 + 13 + 20+ ... + 412
2. sum of 19+15+11+ ... + (-229)
3. sum of -8-2+ 4 + 10 + ... + 142
4. sum of 119 + 129 + 139 + ... + 239
5. sum of - 27 - 19-11-3+ ... + 501
6. sum of the first 75 multiples of 6
7. sum of the first 63 numbers of the series 19 + 15 + 11 +
8. sum of the first 54 numbers of the series 3 + 13 + 23 +
9. sum of the first 100 multiples of 4.
10. sum of the first 126 multiples of 7.
11. sum of the first 53 terms if a = -8 and d = 6.
12. sum of the first 64 terms if a = 11 and d= - 4.
13. sum of the first 72 terms if a, = 4 and d = 5
14. sum of the first 87 terms if a) = -5 and d = 10
15. sum of the first 96 terms if a, = 7 and d=-6​