Similar Triangles??

Question

I could REALLY use some help...PLEASE

Suppose triangle ANC ~ triangle JKL with BC=28, JK=12 & KL=42. Fins the perimeter of triangle ABC if the perimeter of triangle JKL is 72.
is it: 60, 48, 18, or12.

Find the scale factor of triangle DEF to triangle DEF~ triangleXYZ, DE=10, XZ=20, & XY=45?
Is it 1:2, 1:4, 2:9, or 2:11

.Suppose triangle ABC~ triangle GHI with scale factor 3:5, AB=9, BC=18, & AC=21. Find the perimeter of triangle GHI.
iS IT: 28.8, 35, 80, OR 92

Answer 1

I assume you mean ABC rather than ANC in the beginning of the first one. If ABC ~ JKL then AB corresponds to JK, AC to JL and BC to KL. This last pair is the only one for which we have both lengths, so we can establish the scale factor as KL/BC = 42/28 = 3/2. So the perimeter of JKL is 3/2 the perimeter of ABC, in other words the perimeter of ABC is 2/3 (72) = 48.
(Additional note: The lengths given in this question cannot be correct, since for any triangle the longest side must be no more than half the total perimeter, but we are given KL = 42 in a triangle with perimeter 72.)

DEF ~ XYZ: DE corresponds to XY, so the scale factor is 10:45 = 2:9.

ABC ~ GHI, scale factor 3:5. The perimeter of ABC is AB + BC + AC = 48, so the perimeter of GHI is 5/3 (48) = 80.

Answer 2

1) for triangle JKL:
12+42+ x=72
x=18
for triangle ABC:
42/28=18/x
28/42=x/12

so x=8 and 12
lengths for ABC: 8, 28, 12
8+28+12=48 cm//

2)
10:45
2:9//

3) just use the lengths you know for triangle ABC and use it to find that of GHI it into the ratio 3:5
for example, for length AB it would be 15.
add them up and you get 80cm.

dont' count on it though

Answer 3

12/28 = 3/7

Thus perimeter of ABC = 3*72/7 = 30.85

2:9

Perimeter of GHI = 3(9+18+21)/5 = 28.8