I seriously need some help with this math?

Question

David is 5 1/2 feet tall. Goliath is 8 ft tall. If Goliaths shadow is 10 ft tall how long is Davids shadow ?

Please explain how to do it too ! I really dont get it and I would like to know how to get the answer . Please ! help thanks !

Answer 1

David's shadow is 7 1/2 feet.

Goliath is 8 ft tall. Shadow is 10. 10 - 8 = 2 feet difference
If David is 5 1/2 ft tall. Add 2 ft = 7 1/2 ft tall shadow.

Answer 2

All you need to do is set up an equality, when 5.5/X = 8/10, and solve for X
X = Davids shadow
5.5 = david's height in feet
8 = goliaths height in feet
10 - goliaths shadow in feet

(is actually easier to set up as...)
x/5.5 = 10/8
x/5.5 = 1.25 (just in decimal form by division or calculator)
x = 1.25*(multiplied by) 5.5

Gotta use the calculator or work it out, i've unfortunately had a drink or two and for some reason can divide better than multiply and cant really do the math... its gonna be close to 7! Work it out and see what you get!

Remember that David and Goliaths shadows (as it will be for anything that should grow at equal prorportions - the topic of the chapter you are learning) you will need to set up an equality equation (when one side ='s the other side)
when doing this you need to have the equal terms (their heights in feet or their shadows in feet - but could be anything you wanted it to be[as long as it can be represented in the equality format]) .... need to have the equal terms at the same position on the fraction... both heights in the numerator or the denominator and the shadows in the same place as well...

then you just cross multiply (numerator leftside by denomator on the right side = numerator right side by denominator left side) and solve for X (the value that you need to find...)

If that is too confusing then I'm sorry and must've done something wrong but that is the only way I can solve it, hope it helps you out.

Answer 3

You need to form a proportion. This one would be set up kind of like this:

5.5 over x is equal to 8 over 10. It can be flipped, just make sure that the shadows and heights are next to each other (In the fraction)

To solve this, you cross multiply. This will leave you with:

8x=55

Divide 55 by eight to get x by itself.

x=6.875 or 6 and 7/8

Answer 4

goliath -

10 foot shadow is 1.25 times taller than him (10/8)

david -

5.5 foot person times factor of 1.25 = 6.875 feet (6'10.5")

Answer 5

You need to set this up as a proportion. 5.5 feet is to 8 feet, as 10 feet is to what? 5.5/8 = x/10
Then you cross multiply
8x=55
x=6.875

Answer 6

10ft - 8ft = 2ft

5 1/5ft +2ft = 71/2ft

Answer 7

x/5.5 = 8/10

x = (5.5) x (8/10) = 4.4 feet

Answer 8

5.5 8
------------------
x 10
8x=55
8x/8=55/8
x=6 7/8
6.875 ft would be the shadow