Question

Find the sun first 15 terms of
the AP 8,7 1/4,6 1/2,5 3/4
​

Answer 1

a= 8 , d= 29/4 - 8= -3/4 and n= 15

S15 = 15/2 {2a+(n-1)d}

= 15/2 {16+14×-3/4 }

= 15/2 (16+ -10.5)

= 15/2 ×5.5

= 41.25

sum of 15 terms 41.25