Linear equations

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Terminology

Age

14 to 16

Challenge level

Given an equilateral triangle inside an isosceles triangle, can you find a relationship between the angles?
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Fractions of Fractions

Age

14 to 16

Challenge level

If you know that a fraction of X is the same as a different fraction of Y, can you work out X/Y?
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Big Fish

Age

14 to 16

Challenge level

Granny has taken up deep-sea fishing! Last week, she caught a fish so big that she had to cut it into three pieces in order to weigh it...
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A Problem of Time

Age

14 to 16

Challenge level

Consider a watch face which has identical hands and identical marks for the hours. It is opposite to a mirror. When is the time as read direct and in the mirror exactly the same between 6 and 7?
problem

Months and Years

Age

14 to 16

Challenge level

The product of Mary's age at her last birthday and her age in complete months is 1800. How old is Mary?
article
A Method of Defining Coefficients in the Equations of Chemical Reactions

A simple method of defining the coefficients in the equations of chemical reactions with the help of a system of linear algebraic equations.
problem
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Leonardo's Problem

Age

14 to 18

Challenge level

A, B & C own a half, a third and a sixth of a coin collection. Each grab some coins, return some, then share equally what they had put back, finishing with their own share. How rich are they?