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### Speedy summations

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

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Speedy summations

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

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Summing Consecutive Numbers

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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?

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Light the Lights Again

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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?

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Slick Summing

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

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Handshakes

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

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Mystic Rose

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

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Triangular Clock

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?

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Triangle Numbers

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Take a look at the multiplication square. The first eleven triangle
numbers have been identified. Can you see a pattern? Does the
pattern continue?

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Route to infinity

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Can you describe this route to infinity? Where will the arrows take you next?

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Factors and Multiples Puzzle

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Using your knowledge of the properties of numbers, can you fill all the squares on the board?