Question

How many terms of the geometric progression 1 + 4 + 16 + 64 + ........ must be added to get sum equal to 5461 ?

Answer 1

let n terms make it sum 5461 .

now ,first term ,a =1 , common ratio ,r =4 .

then we can say , =5461

= 4ⁿ-1 = 16383

= = 16384

= n =7 . so , 7 terms of his series will make the sum of 5461