Triangle numbers

There are 31 NRICH Mathematical resources connected to Triangle numbers

problem

Speedy summations

Age

16 to 18

Challenge level

Watch the video to see how to add together an arithmetic sequence of numbers efficiently.

problem

Favourite

Summing Consecutive Numbers

Age

11 to 14

Challenge level

15 = 7 + 8 and 10 = 1 + 2 + 3 + 4. Can you say which numbers can be expressed as the sum of two or more consecutive integers?

problem

Favourite

Light the Lights Again

Age

7 to 11

Challenge level

Each light in this interactivity turns on according to a rule. What happens when you enter different numbers? Can you find the smallest number that lights up all four lights?

problem

Favourite

Slick Summing

Age

14 to 16

Challenge level

Watch the video to see how Charlie works out the sum. Can you adapt his method?

problem

Favourite

Handshakes

Age

11 to 14

Challenge level

Can you find an efficient method to work out how many handshakes there would be if hundreds of people met?

problem

Favourite

Mystic Rose

Age

14 to 16

Challenge level

Use the animation to help you work out how many lines are needed to draw mystic roses of different sizes.

problem

Triangular Clock

Age

11 to 14

Challenge level

Trinni rearanges numbers on a clock face so each adjacent pair add up to a triangle number... What number did she put where 6 would usually be?

problem

Favourite