Solve the system of equations to find the values of x, y and z: xy/(x+y)=1/2, yz/(y+z)=1/3, zx/(z+x)=1/7
If all the faces of a tetrahedron have the same perimeter then show that they are all congruent.
A group of 20 people pay a total of £20 to see an exhibition. The admission price is £3 for men, £2 for women and 50p for children. How many men, women and children are there in the group?
In the final applet below we have a quadrilateral. Here you see
that there are 4-sided polygons where the 4 circles are not all
tangent to one another. Can you make the red and green circles lie
on top of one another? Then you have made all the circles tangent
to their neighbours.
Created with GeoGebra