Simplify $\frac{{{(p-r)}^{2}}-{{r}^{2}}}{2{{p}^{2}}-4pr}$

If 20(mod 9) is equivalent to y(mod 6), find y

Detemine $M'\cap N$from the Venn diagram

The perimeter of a sector of a circle of radius 21cm is 64cm. Find the angle of the sector. Take [$\pi=\tfrac {22}{7}$ ].

In the diagram, MOPQ is a trapezium with $QP\parallel MO,$$MQ\parallel NP$$NQ\parallel OP$. $\left| OP \right|=9cm$and the height of $\vartriangle QNP=6cm$. Calculate the area of the trapezium

Express 1975 correct to 2 significant figures

A sphere of radius r cm has the same volume as the cylinder of radius 3cm and height 4cm. Find the value of r

If ${{\log }_{2}}(3x-1)=5$, find x

The marks of eight students in a test are: 10, 4, 5, 14, 13, 16 and 17. Find the range.

A fair die is thrown two times. What is the probability that the sum of the scores is at least 10?