Question

If a=3 and t6 = 27 find the sum of first 6 terms of the A.P​

Answer 1

S6 = n/2.(2a+(n-1).d
S6 = 6/3.2(3)+(6-1).d
27= 2.(6+5d)
27= 12+5d
27-12= 5d
15= 5d
D= 3

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Answer 2

Answer:

d=4.8

ans .90

Step-by-step explanation:

tn=a+(n-1)d

t6=3(6-1)d

27=3+5d

27-3=5d

24/5=d

4.8=d

now,

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

S6=6/2(2(3)+(6-1)4.8)

S6=3(6+5×4.8)

=3(6+24)

=3(30)

S6=90