Determine the sum of the arithmeitc series.Using a specific formula.?

Question

The formula is a +tn(n) divided by 2
a - the first number
tn - last number
n - number of numbers in the sequence

The series is this - 1, 5, 9, 13,....... all the way up to 97.

Answer 1

You've got the right formula, just need to plug and chug.

There are 25 numbers in the sequence. You can see this because if you add 3 to each number the sequence would be

4, 8, 12, 16, ..., 100

and then if you divide each number by 4 the sequence would be

1, 2, 3, 4, ..., 25.

so obviously there are 25 of them. ;-)

Now to plug and chug:
the answer = (a + tn) (n) / 2
= (1 + 97) (25) / 2
= 1225

Answer 2

1214.5