we know that a1=1 a2=3 a3=9 a2/a1=3/1----> 3 a3/a2=9/3----> 3 common ration r is equal to 3 number of terms n is 12
The Sum of geometric series is given by the formula Sum=a1*[1-r^n]/[1-r] Sum=1*[1-3^12]/[1-3]-----> Sum=[1-3^12]/[1-3]----> [3^12-1]/[3-1] Sum=531440/2-----> 265720
