Question

sum of first 5 terms of an a.p is 150 and the sum of first 10 terms is 550 then what is the 3rd and 8th terms of the sequence​

Answer 1

Step-by-step explanation:

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

150=5/2{2a+4d}

300/5=2a+4d

2a+4d=60..…...(i)

and

550=10/2{2a+9d}

{2a+9d}=110....….....(ii)

multiply 2 from i. and sub. ii. from i,we get.

a=10,d=10.

Tn=a+2d

T3=30

T8=80.

hence 3rd and 8th terms are 30 and 80