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Mathematics 6 Online
OpenStudy (anonymous):

geometry please help :) Two similar solids are shown below. Two similar solids are shown. The length of the smaller solid is 5 feet and its volume is 875 cubic feet. The length of the bigger solid is 7 feet. Its volume is not known. What is the volume of the larger solid? 1750 ft3 1000 ft3 7000 ft3 3500 ft3

OpenStudy (anonymous):

OpenStudy (anonymous):

What is the ratio of the lengths (small to large).

OpenStudy (anonymous):

?

OpenStudy (anonymous):

im not sure what your asking. i just attached a picture

OpenStudy (anonymous):

I am confused too. In the problem it says the length of the larger solid is 7feet. In the picture it shows a length of 10 feet. Which one is correct?

OpenStudy (anonymous):

im sorry my fault. the question is, What is the volume of the larger solid? ignore the original post.

OpenStudy (jdoe0001):

I'd defer to the picture, though it could be 2 valid exercises mixed up

OpenStudy (anonymous):

my fault, the picture is correct

OpenStudy (anonymous):

Okay, I am ignoring the original post. The ratio of the lengths of the small solid to the large solid is 5 to 10 or 5:10 = 1:2.

OpenStudy (anonymous):

So the ratio of the lengths is 1:2. If I remember correctly my geometry textbook calls this the "scale factor".

OpenStudy (jdoe0001):

or \(\bf \cfrac{10}{5} = \cfrac{v_2}{v_1}\)

OpenStudy (anonymous):

What will the ratio of the volumes be?

OpenStudy (anonymous):

incorrect.

OpenStudy (anonymous):

@jdoe0001 you are close but not quite correct. The ratio of the volumes is not equal to 10:5 or 5:10.

OpenStudy (anonymous):

to get the ratio of the volumes you must CUBE the ratio of the lengths.

OpenStudy (anonymous):

ratio of volumes = (ratio of lengths)^3 = (1:2)^3 = 1:8

OpenStudy (jdoe0001):

hmmm, that sounds right :)

OpenStudy (jdoe0001):

\(\bf \cfrac{10^3}{5^3} = \cfrac{v_2}{v_1}\)

OpenStudy (anonymous):

\[\frac{ 8 }{ 1 } = \frac{ v _{2} }{ v _{1} }\]

OpenStudy (anonymous):

Yes, @jdoe0001, that it correct, however I present the same equation in simplified form.

OpenStudy (jdoe0001):

indeed

OpenStudy (anonymous):

so similar means in this case that all the lenghs are 2:1 ?

OpenStudy (anonymous):

How's it going @LaurenAshley1201 ?

OpenStudy (anonymous):

Yes @nistal.

OpenStudy (anonymous):

@LaurenAshley1201 \[\frac{ 8 }{ 1 } = \frac{ v_{2} }{ 875 }\]

OpenStudy (anonymous):

Cross multiply to find your volume for the larger solid. Ask me a question if this does not make sense.

Directrix (directrix):

>The length of the bigger solid is 7 feet. (posted) On the diagram, the length is shown as 10. So, I'm assuming the length of the second solid is 10. I need to recalculate.

Directrix (directrix):

Theorem: If two solids are similar, the cube of the scale factor of the two solids is equal to the ratio of the volumes. (5/10)³ = 875/V where V is the volume of the larger solid 1/8 = 875/V @LaurenAshley1201 Solve the equation for V.

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