# Question on Triangles?

Two triangles are similiar. The lengths of the sides of the smaller triangle are 4,6,7. The longest side of the larger triangle are 21. What is the perimeter of the larger triangle?

### 7 Answers

- Anonymous10 years agoFavorite Answer
since 7 is the longest on the smaller it corresponds to the 21 on the larger, and you figure out that u multiply 7 by 3 to get 21 so you multiply 4 and 6 by 3 to get 12 and 18 so u add 12, 18, and 21 which equals 51

- Dr PiLv 410 years ago
Answer : Perimeter = 51

Solution:

Let p = perimeter of the smalller tiangle

Let P = perimeter of the larger triangle

They gve you all of the sides of the smaller triangle which you can add them all up to find p which is 17. They give you th longest side of the larger triangle which is 21 while the larger side of the smaller triangle is 1/3 of 21 (7) so you can assume they multiplied 7 by 3 to get 21. So now you can just multiply p by 3 to find P.

(P/p) = (21/7)

p = 4+6+7 = 17

P = (17)x(3)

P = 51

Source(s): Junior in Ap Calculus Ab - 10 years ago
When two triangles are similar, it means their dimensions are proportionate. If the longest side of the larger triangle is 21, it means that the smaller triangle's dimensions were multiplied by 3. (7 * 3 = 21).

Therefore the dimensions of the larger triangle will be 12, 18, 21

The perimeter would be 12 + 18 + 21 = 51.

- 10 years ago
Answer : P = 51

Solution:

Let p = perimeter of the smalller tiangle

Let P = perimeter of the larger triangle

Now, since it is given that 21 is the longest side of the larger side. we can use the principle of similar triangles, since 7 is the longest side of the smaller triangle, we can use this relationship:

(P/p) = (21/7)

since all sides of the smaller triangle is given, we can get p

p = 4+6+7 = 17

substituting into the equation

(P/17) = (3)

P = (17)x(3)

P = 51

Source(s): I'm an engineering student - How do you think about the answers? You can sign in to vote the answer.
- 10 years ago
51

If the triangles are similar, all the sides of the larger one will be 3 times the smaller. 12, 18, and 21.

Source(s): Helping my kids with geometry - BieberLv 610 years ago
This just means that this triangle is 3 times bigger, so:

(4 * 3) + (6*3) + (7*3) =

12 + 18 + 21 =

51

Have a great day! :-)