Posted by **Karen** on Wednesday, October 9, 2013 at 8:30pm.

At the ruins of Caesarea, archaeologists discovered a huge hydraulic concrete block with a volume of 945 cubic meters. The block's dimensions are x meters high by 12x - 15 meters long by 12x - 21 meters wide. What is the height of the block?

I have no idea how to do this. Can someone please help me?

- math -
**Reiny**, Wednesday, October 9, 2013 at 9:17pm
remember , volume = lwh

x(12x-15)(12x-21) = 945

simplifying a bit

x(3)(4x - 5)(3)(4x-7) = 945

x(4x-5)(4x-7) = 105

16x^3 -48x^2 +35x - 105=0

by grouping ...

16x^2(x - 3) + 35(x-3) = 0

(x-3)(16x^2 + 35) = 0

x = 3 or x^2 = -35/16 , which is not real

so the only real solution is x = 3

so the block is 3 m high,

- math -
**Karen**, Wednesday, October 9, 2013 at 9:22pm
How do you get 105?

- math -
**Reiny**, Wednesday, October 9, 2013 at 9:23pm
I divided both sides by 9

945÷9=105

notice the (3)(3) is gone on the left side

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