which is the 5th triangular number?

Answer 1

Imagine snooker balls in triangle.

1st row 1
2nd row 2
3rd row 3
4th row 4
5th row 5
etc

So n th triangular number is sum of first n rows =15 if 5 rows.

Also formula is n(n +1)/2 for nth triangular number.

Note as either n or n + 1 must be even this is always a whole number.

Answer 2

Triangular numbers are found by the sumof all values of r from r=1 to n, where n is the required value (in the case you gave above, 5). This works out as having a value of
n(n+1)/2

So in this case, you get a value of 5 * 6 / 2 = 15.

Answer 3

15

Answer 4

It is either 15 or 21, depending whether or not 1 is counted as being triangular.

Answer 5

15
if you start at one then add 2, to get 3, then add 3, to get 6, etc. adding on one more each time, wel thats the simple version anyhow and it works for th elow numbers, it would take a while to work out the hundreth triangular number though!
hope you find your answer.

Answer 6

1
3
6
10
15

Therefore Answer is 15

Answer 7

they answer is 15
hope this helps