A pie chart (or a circle chart) is a circular statistical graphic, which is divided into slices to illustrate numerical proportion. In a pie chart, the arc length of each slice (and consequently its central angle and area) is proportional to the quantity it represents.

When letters in a formula are replaced by numbers, it is called substitution.

For the purpose of measuring time, the Earth's surface is divided into

24 equal wedges of 15 each called a time zone, beginning at Greenwich, London (GMT). As you pass over each zone to the east you add 1 hour to GMT, and as you pass over each zone to the west you subtract  1 hour from GMT.

Standard form is a way to write really large or very small numbers.
It follows the format a × 10ⁿ  So it can be Squared, Cubed And even further!
Standard form is often used in engineering, construction and in the medical profession.

Here is a video to help learn it!
https://www.bbc.co.uk/bitesize/topics/z2mf9j6/articles/zh4ny4j