Question

I ANSWER ALL THE QUESTIONS: (4 X 3 = 12)
1. In an AP, if a=15, d=3 and an= 60, find n and Sn.
(or)​

Answer 1

Answer:

a=15, d=3, an=60

an = a+(n-1)d

60 = 15+(n-1)3

60 = 15+3n-3

60 = 12+3n

60-12 = 3n

48 = 3n

n = 48/3

n = 16

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

= 16/2[2x15+(16-1)x3]

= 8[30+45]

= 8[75]

= 600 ans...