What is the sum of the first 100 numbers of the following sequence- 4,12,36, 108, .........

This question is about geometric sequences. The first step in solving this question is identifying that each term is multiplied by 3 to get to the next term.Therefore since the formula for finding the sum of a certain number of terms is - a(1-rⁿ)/1-r.You would just put the numbers in to the formula. A is the first number so 4, r is the factor by which each term is multiplied by so 3, n is the number of terms which is 100.
If your calculations are correct you should get an answer of 1.03x10⁴⁸