Summation of series

There are 32 NRICH Mathematical resources connected to Summation of series
Succession in Randomia
problem

Succession in Randomia

Age
16 to 18
Challenge level
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By tossing a coin one of three princes is chosen to be the next King of Randomia. Does each prince have an equal chance of taking the throne?
Harmonically
problem

Harmonically

Age
16 to 18
Challenge level
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Is it true that a large integer m can be taken such that: 1 + 1/2 + 1/3 + ... +1/m > 100 ?
Production Equation
problem

Production Equation

Age
16 to 18
Challenge level
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Each week a company produces X units and sells p per cent of its stock. How should the company plan its warehouse space?
Picturing Square Numbers
problem

Picturing Square Numbers

Age
11 to 14
Challenge level
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Square numbers can be represented as the sum of consecutive odd numbers. What is the sum of 1 + 3 + ..... + 149 + 151 + 153?
Clickety Click and all the Sixes
problem

Clickety Click and all the Sixes

Age
16 to 18
Challenge level
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What is the sum of: 6 + 66 + 666 + 6666 ............+ 666666666...6 where there are n sixes in the last term?
Seriesly
problem

Seriesly

Age
16 to 18
Challenge level
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Prove that k.k! = (k+1)! - k! and sum the series 1.1! + 2.2! + 3.3! +...+n.n!
Reciprocal Triangles
problem

Reciprocal Triangles

Age
16 to 18
Challenge level
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Prove that the sum of the reciprocals of the first n triangular numbers gets closer and closer to 2 as n grows.
More Polynomial Equations
problem

More Polynomial Equations

Age
16 to 18
Challenge level
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Find relationships between the polynomials a, b and c which are polynomials in n giving the sums of the first n natural numbers, squares and cubes respectively.
Picture Story
problem

Picture Story

Age
14 to 16
Challenge level
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Can you see how this picture illustrates the formula for the sum of the first six cube numbers?