Question

Find the sum of the sequence.
39 +40 +41 +42 + ... + 138

Answer 1

Sol1 you can use "first(first+last)/2" is 138(138+1)/2 - 38(38+1)/2 = 8850

Sol2 or you can look this 39+40+41+....+100+(100+1)+(100+2)+....+(100+38) = 1+2+3+.....+99+100+100(38) = 5050+3800 =8850