Video Transcript
Find the perimeter of the
rectangle.
First of all, what does perimeter
mean? The perimeter is the distance all
the way around an object. We find the perimeter by adding up
all the sides. To find the perimeter of a
rectangle, we could add its four sides: side one plus side two plus side three plus
side four. Or when we’re working with
rectangles, we can multiply two times the length plus the width.
Let’s talk about why. If the length is 15 centimeters and
the width is 10 centimeters, the side across from the 15-centimeter length is also a
length of 15 centimeters. The side across from the width of
10 centimeters is another width of 10 centimeters.
Let’s then put our two different
formulas side by side and solve them. The first version for solving the
perimeter is to add up all four sides. We can start at the top. 15 plus 10 plus 15 plus 10 equals
the perimeter. Now let’s fill in our second
equation. The perimeter equals two times the
length 15 plus the width of 10.
For the first formula, we can add
up 15 and 10 plus 15 plus 10. Five plus zero plus five plus zero
equals 10. We write down our zero and carry
our one. One plus one plus one plus one plus
one equals five. Our first formula tells us that the
perimeter is 50 centimeters.
Let’s try the second option. 15 plus 10 is in parentheses. So we do that first. 15 plus 10 is 25. Two times 25 equals 50. Both formulas give us an outcome of
50 centimeters. The perimeter, the distance all the
way around this rectangle, is 50 centimeters.
