In an increasing geometric series, the sum of the second and the sixth term is 252  and the product of the third and fifth term is 25. Then, the sum of 4th, 6th and 8th terms is equal to :

Given ar+ar5=252 and ar2ar4=25⇒ar3=5            Substitute  a=5r3in the above equation.                                                5r3×r+5r3×r5=2521r2+r2=52r2=2            Hence, T4+T6+T8=ar31+r2+r4=51+2+4=35