Find the sum of the series 99+95+91+87+… to 20 terms.

Find the sum of the series 101+99+97+95+…..+43

Find the sum of the series 3 + 7 + 13 + 21 + 31 + … to n terms . Find the sun when n=20

Find the sum of the series : 3,-4,(16)/(3),... to 2n terms.

The sum of 40 terms of an arithmetic progression is 430 and the sum of 60 terms is 945. Find the 20th term.