Question

Sum of the first 10 terms of the A.P-0.5,-1.0,-1.5 ...........?

Answer 1

a= -0.5
d= -0.5
n= 10

S= n/2 (2a+(n-1)d)

= 10/2 (-1 + 9 × -0.5)
= 5 ( -1 -9/2)
= 5 (-5.5)
= -27.5