Perimeter/area Flashcards
How do you calculate the perimeter of a square?
4xs (s is short for side)
Ex:s=5
5x4
20
Define a perimeter:
A perimeter is the length of the outline of a geometrical figure.
How do you calculate the perimeter of a rectangle?
There are three methods: -h+h+w+w (h is short for height, w is short for width) -hx2+wx2 -(h+w)x2 Ex:h=4 w=5 (4+5)x2 9x2 18
Perimeter of a square of s=6?
6x4
24
Perimeter of a rectangle h=7 w=10?
(7+10)x2
17x2
34
Define area:
Area is all the part that is inside the geometrical figure.
How do you calculate the area of a square?
sxs
Ex:s=5
5x5=25
How do you calculate the area of a rectangle?
hxw
Ex:h=6 w=5
6x5=30
What is pi ( pronounciation: pie)?
Pi is named after the greek letter pi. In maths, pi is equal to ~3.14.Actually, it is impossible to say exactly what pi is equal to since the digits go on for ever with no repetition at all. The first digits are 3.14159265358…
Pi is used for a lot of things, but mainly for measuring the perimeter and area of circles.
The first people to use it were the Greeks.
Define the radius of a circle:
The radius is the line that goes from O to the edge of the circle.The radius itself is written r. The measure of the radius is written as R.
Define a chord in a circle.
A chord is the line that goes from one edge of the circle to the other.
Define the diameter in a circle:
A diameter is the longest chord, it passes by O and is exactly the double of the radius.
How do you measure the perimeter of a circle?
Pi x r x 2
Ex: r=5
Pi x 5 x 2
Pi x 10 This is the exact value.
You cannot get closer to the exact value.
3.14x10
31.4 This is the approximate value.
How do you measure the area of a DISK (not a circle!)
Pi x (r squared) Ex: r=5 Pi x (5x5) Pi x 25 This is the exact value. 3.14x25 78.5 This is the approximate value.
