I need help with my math worksheet. I wasn't in class that day....

Ok so I had to do a worksheet in math but i was taking a test that i had not finished so she did not teach me how to do it. I know how to solve it with pythagorean theorem but we aren't supposed to know that (i learned it before) Here is an example ( PLEASE SHOW YOUR WORK AND EXPLAIN TO ME!!! otherwise i will be totally lost.. :) The 2nd one is esp. confusing to me...


A giraffe is 18 feet tall and casts a shadow of 12 feet. Corry casts a shadow of 4 feet. How tall is corry?


When a Ferris wheel casts a 20-meter shadow a man 1.8 meters tall casts a 2.4 meter shadow. How tall is the Ferris wheel.

Draw a diagram:
http://i39.tinypic.com/rwp07l.png

In diagram above, since sun shines down on giraffe and Corry at same angle
∠A = ∠D
Since both triangles are right-triangles
∠B = ∠E
Remaining angles must also be congruent
∠C = ∠F

Therefore triangle ABC is similar to triangle DEF, i.e.
DE/AB = EF/BC = DF/AC

Let x = DE = Corry's height. Then we have:
DE/AB = EF/BC
x/18 = 4/12
x/18 = 1/3
x = 6 ft

You are correct, but I'm not sure how you found correct result without using similar triangles. You cannot use Pythagorean theorem, since you don't know length of hypotenuse DF.


Use same method for finding height of Ferris wheel
height of Ferris wheel / height of man = shadow of ferris wheel / shadow of man
height of Ferris wheel / 1.8 = 20 / 2.4
height of Ferris wheel = 1.8 * 20 / 2.4 = 15 m

Mαthmφm

I won't give you the answer, but show you how to set it up.

Draw Corry, and his shadow. Now make a line from Corry's head to his shadow's head. This creates a triangle.

Now draw a similar triangle with the giraffe. The giraffe's triangle will be larger, but both triangles will be the *same* shape, with the same angle. Since the sun is in the same place in the sky.