How to Find the nth Triangular Number

The video tutorial explains how to find the NTH triangular number by visualizing dots as right-angled triangles and then forming rectangles. It introduces a formula to calculate triangular numbers and provides an example with n=4. The video concludes with practice questions for viewers to solve.

What is the first step in finding the NTH triangular number?

• Rearrange dots into a square

• Rearrange dots into a right-angled triangle

• Double the number of dots

• Subtract dots from a rectangle

How do you form a rectangle from the triangular number dots?

• By doubling the dots

• By tripling the dots

• By halving the dots

• By adding more dots

What is the formula used to find the NTH triangular number?

• N * N / 2

• N + (N + 1) / 2

• N * (N - 1) / 2

• N * (N + 1) / 2

If the 4th triangular number is calculated, how many dots are in the rectangle before halving?

• 25

• 20

• 15

• 10

What should you do after calculating the number of dots in the rectangle to find the triangular number?

• Double the number of dots

• Add more dots

• Halve the number of dots

• Subtract the number of dots