Q. 6. If the sum of first 13 terms of an A.P. is 91 and sum of its first 30 terms is 465. Find the sum of its 50 terms. Q. 7. The sum of three numbers which are in A.P. is 9 and sum of their squares is 35. Find the numbers. Q. 8. Divide 32 into 4 parts such that they are in AP and the ratio of the product of first term and fourth terms = product of second and third terms is equal to 7/15. Q. 9. If the pth, ath, rth terms of an AP are a,b,c, then prove a(q-r) + b(r-p) = c(q- p)