## Degrees

Degrees are a unit of measurement for a circle. There are 360 degrees in a circle. Degrees are used to express rotation. For example, if somebody says they are turning 180 degrees, it means they are turning around to face the opposite direction, since 180 degrees is 50% of a circle.
To convert degrees to a percent of a circle, divide degrees by 360 to get a decimal, and multiply the decimal by 100 to get a percent. For example:
```degrees = 180
decimal = 180 ÷ 360 = 0.5
percent = 0.5 × 100 = 50
```
To convert a percent of a circle to degrees, divide the percent by 100 to get a decimal, and multiply the decimal by 360 to get degrees. For example:
```percent = 25
decimal = 25 ÷ 100 = 0.25
degrees = 0.25 × 360 = 90
```
Degrees are also used for geographic coordinates, which makes sense since going around the earth is essentially going around a circle. There are two parts to the geographic coordinate system: latitude and longitude. Latitude measures the distance from the equator, which divides the earth into northern and southern hemispheres. Longitude measures the distance from the prime meridian, which divides the earth into eastern and western hemispheres.
Latitude is expressed as a number of degrees north or south, and ranges from 0 to 90 in both directions. Latitude of 0 degrees is at the equator, 90 degrees north is at the north pole, and 90 degrees south is at the south pole. Longitude is expressed as a number of degrees east or west, and ranges from 0 to 180 in both directions. Longitude of 0 degrees is at the prime meridian, which runs through Greenwich, England. Locations east of the prime meridian are expressed as degrees east, and locations west of the prime meridian are expressed as degrees west. East and west longitudes meet at 180 degrees, which runs mostly through the Pacific Ocean between China and the USA.

### Exercise 1 of 6

What percent of a circle is 270 degrees?

### Exercise 2 of 6

What percent of a circle is 1,080 degrees?

### Exercise 3 of 6

How many degrees is 12.5% of a circle?

### Exercise 4 of 6

How many degrees is 37.5% of a circle?

### Exercise 5 of 6

How many degrees of longitude does the earth rotate in one hour?

### Exercise 6 of 6

Recall from above that Greenwich, England is at longitude 0 degrees. The border between northern California and Nevada is at longitude 120 degrees west. This means that northern California is 120 degrees west of Greenwich. How many hours do you have to wait for the sun's position in northern California to be the same as it was in Greenwich? Said another way, how many hours does it take for the earth to rotate 120 degrees?