Conjecturing and generalising

There are 405 NRICH Mathematical resources connected to Conjecturing and generalising
Cubes within Cubes revisited
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Cubes within cubes revisited

Age
11 to 14
Challenge level
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Imagine starting with one yellow cube and covering it all over with a single layer of red cubes, and then covering that cube with a layer of blue cubes. How many red and blue cubes would you need?
Mirror, mirror...
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Mirror, mirror...

Age
11 to 14
Challenge level
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Explore the effect of reflecting in two parallel mirror lines.
Consecutive negative numbers
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Consecutive negative numbers

Age
11 to 14
Challenge level
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Do you notice anything about the solutions when you add and/or subtract consecutive negative numbers?
Handshakes
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Handshakes

Age
11 to 14
Challenge level
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Can you find an efficient method to work out how many handshakes there would be if hundreds of people met?
How Odd
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How odd

Age
5 to 7
Challenge level
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This problem challenges you to find out how many odd numbers there are between pairs of numbers. Can you find a pair of numbers that has four odds between them?
What was in the Box?
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What was in the box?

Age
5 to 7
Challenge level
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This big box adds something to any number that goes into it. If you know the numbers that come out, what addition might be going on in the box?
Pebbles
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Pebbles

Age
7 to 11
Challenge level
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Place four pebbles on the sand in the form of a square. Keep adding as few pebbles as necessary to double the area. How many extra pebbles are added each time?

Dozens
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Dozens

Age
7 to 14
Challenge level
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Can you select the missing digit(s) to find the largest multiple?

1 Step 2 Step
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1 step 2 step

Age
11 to 14
Challenge level
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Liam's house has a staircase with 12 steps. He can go down the steps one at a time or two at time. In how many different ways can Liam go down the 12 steps?
Picturing Triangular Numbers
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Picturing triangular numbers

Age
11 to 14
Challenge level
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Triangular numbers can be represented by a triangular array of squares. What do you notice about the sum of identical triangle numbers?