Question

find the sum of the first 20 terms of the arithmeticprogression 1 + 4 + 7 + ....mmm​

Answer 1

Answer:

590

Step-by-step explanation:

the formula for sum of a arithmetic progression with 1st term 'a' and common difference 'd' for 1st n'' terms is given by

sum = n*[2*a + (n-1)*d]/2

here a = 1, d = 3, n = 20

hence the sum  = 20*[2*1 + (20-1)*3]/2 = 20*[2+19*3]/2 = 590