Question

find n if the sum to n terms of AP 1,4,7...............is 145

Answer 1

Hello mate

Here is your answer

Answer 2

first term is - 1
second term- 4
therefore difference is - 3
last term-. 145
according to the formula
tn= a+(n-1)d
145=1+(n-1)*3
145-1=(n-1)*3
144/3=n-1
48+1=n
therefore n=49