Question

Answer in 3940.plz solve this

Answer 1

let the sum of first five terms =s5 and seven terms =s7 
the formula for sum of first n terms = sn=n/2[2a+(n-1)d] n= number of terms, a is the first term and d is the difference 
s5+s7=167= 5/2[2a+4d]+ 7/2[ 2a+ 6d] =167 
5[a+2d]+7[a+3d]=167 
5a+10d+7a+21d=167 
12a+31d=167 


235=10/2[2a+9d] 
235=5[2a+9d] 
235=10a+45d 
2a+9d=47(dividing by 5) 
solving the two equations we get d=5 a=1 
sum of first forty terms = 40/2[2+19*5] 
20[2+95] 
1940

Answer 2

answer of this question is1940