Question

if 12th term of AP is -13 and the sum of first 4 terms is 24 then find sum of first 10 terms​

Answer 1

Answer:

713.4

Step-by-step explanation:

As given,

12th term= 213

⇒a+11d=213       --------1

and

sum of 4 terms =24

⇒n/2[2a+(n-1)×d]=24

=》4/2[2a+(4-1)×d]=24

=》2(2a+3d)=24

=》2a+3d=12 ----------2

by solving equation 1 and 2

a= -26.67

d=21.78

so, sum of 10 terms=10/2[2×(-26.67)+9×21.78]

=》5[-53.34+196.02]

=》5×142.68

=》713.4

Hope it helped you....