Perimeter of a square
Finding the perimeter of a square when a side is given and finding the length of a side when the perimeter is given are the goals of this lesson
Given a square with side s, the perimeter (P) or distance around the outside of the square can be found by doing
P = s + s + s + s = 4 × s
Find the perimeter of a square when s = 3 cm
P = 4 × s = 4 × 3 = 12 cm
Notice that it is perfectly ok to do P = 3 + 3 + 3 + 3 = 12
However, it is usually easier and quicker to do 4 times 3 than adding 3 four times
Find P when s = 5 cm
P = 4 × s = 4 × 5 = 20 cm
Find P when s = 2/8 cm
P = 4 × s = 4 × 1/8 = (4/1) × (2/8) = (4 × 2)/ ( 1 × 8 )= 8/8 = 1 cm
A square has a perimeter of 12 inches. Find s
Here, given the perimeter, you are asked to find the length of a side of the square.
We know that P = 4 × s
You should replace P by 12 because that is what they gave you.
So, 12 = 4 × s
The problem becomes a
multiplication equation that you need to solve
However, you can solve this equation with mental math. Replace s by a question mark(?) and ask yourself the following:
4 times ? = 12 or 4 times what will give me 12? The answer is 3, so s = 3
The perimeter of a square is 64 cm. What is the length of one side?
Again, since P = 4 × s, we get 64 = 4 × s after replacing P by 64
Ask yourself 4 times what will give me 64? Since 4 times 16 is 64, s = 16
You don't have to guess 4 times what will give 64. You can also divide 64 by 4 to get 16
In fact, whenever you are looking for s and P is a big number, you should always divide p by 4 to get s
Notice that to get the perimeter of a rhombus, you can do the exact same thing we did above for the square.
Since just like the square, all sides of a rhombus are equal, there is absolutely no difference as far as getting the perimeter!
Therefore, P is also equal to s + s + s + s = 4 × s

Jun 08, 17 01:52 PM
Learn quickly how to multiply using partial products
Read More
New math lessons
Your email is safe with us. We will only use it to inform you about new math lessons.