### Video Transcript

Triangles ๐ด๐ต๐ถ and ๐ธ๐ท๐น are
congruent. What is the perimeter of triangle
๐ด๐ต๐ถ?

So here we have two triangles which
weโre told are congruent. That means theyโre the same shape
and size. More specifically, we can say that
corresponding sides are equal and corresponding pairs of angles are equal. We might therefore look at our
triangles and note that we have a side of 10 centimeters, a side of 11 centimeters,
and, on triangle ๐ด๐ต๐ถ, we have a side of eight centimeters. We might guess that side ๐ธ๐ท is
eight centimeters, but letโs check.

We can use the congruency
relationship and the order of letters to help us here. If we look at side ๐ท๐น on triangle
๐ธ๐ท๐น, thatโs going to be congruent with side ๐ต๐ถ on triangle ๐ด๐ต๐ถ. So that means theyโll both be 11
centimeters long. Next, if we look at side ๐ธ๐น on
triangle ๐ธ๐ท๐น, thatโs going to correspond with the length ๐ด๐ถ on triangle
๐ด๐ต๐ถ. And that means that ๐ด๐ถ is also 10
centimeters long.

The two final sides on each
triangle, thatโs side ๐ด๐ต on triangle ๐ด๐ต๐ถ and side ๐ธ๐ท on triangle ๐ธ๐ท๐น, will
also be the same length of eight centimeters. Weโre asked to find the perimeter
of triangle ๐ด๐ต๐ถ. Thatโs the distance around the
outside. So we take our three lengths of 10,
11, and eight centimeters and add them together, which gives us a perimeter of 29
centimeters.

Note that we have the length unit
of centimeters rather than square centimeters, which would be an area. Note that if we choose triangle
๐ธ๐ท๐น instead, we wouldโve found the same value for the perimeter as two congruent
triangles would have the same perimeter.