Question 1187757
<br>
Let x = height<br>
Then from the given information<br>
2x+5 = length
5x = width<br>
The volume is length times width times height:<br>
V = x(2x+5)(5x)<br>
or<br>
V = 10x^3+25x^2<br>
We are to find x and thus the dimensions if the volume is 180, and if the volume is 495.<br>
One way to find the answers would be to solve the equations 10x^3+25x^2=180 and 10x^3+25x^2=495.  But solving a cubic equation is mostly a matter of trial and error.<br>
A much easier method, since the given volumes are whole numbers, is to look for whole number values of x which make the product (x)(2x+5)(5x) equal to 180 or 495.<br>
Clearly x has to be small; so we can just try x=1, 2, 3... to find the answers.<br>
x=1: (x)(2x+5)(5x) = (1)(7)(5) = 35
x=2: (x)(2x+5)(5x) = (2)(9)(10) = 180
x=3: (x)(2x+5)(5x) = (3)(11)(15) = 495<br>
We have found both the required volumes....<br>
ANSWERS:
volume 180 cm^3: dimensions 2cm by 9cm by 10cm
volume 495 cm^3: dimensions 3cm by 11cm by 15cm<br>