Question

The volume of a rectangular prism is given by the formula V = lwh, where l is the length of the prism, w is the width, and h is the height. Which expression represents the volume of the following rectangular prism?
h=2x+9
l= x+2
w= 3x

A) 2x^2+13x+18
B) 6x^3+27x^2+54x
C) 6x^3+39x^2+54x
D) 18x^4+117x^3+162x^2

Answer 1

(2x+9) * (x+2) * (3x) =
(2x^2 + 4x + 9x + 18) * (3x) =
6x^3 + 12x^2 + 27x^2 + 54x =
6x^3 + 39x^2 + 54x

Answer is C

Answer 2

Solution: As given, Volume of a rectangular prism is given by the formula V = l w h, where l is the length of the prism, w is the width, and h is the height.

also , h=2x+9

l= x+2

w= 3 x

So, volume of prism= (2 x+9)(x+2)(3 x)= (3 x)(2 x+9)(x+2)→Using associative property

       =3 x[2 x(x+2)+9(x+2)]→Using (x+a)(x+b)= x(x+a)+a(x+b)=x²+(a+b)x+ab

      = 3 x [ 2 x²+ 4 x+ 9 x+18]

      = 3 x[ 2 x² +13 x+18]

 = (3 x)(2 x²) + (3 x)×(13 x) + (3 x)×(18)→ Using distributive property

= 6 x³+ 39 x² + 54 x → [ use [tex]x^{m} \times x^{n}= x^{m+n}[/tex]

Option (C) is correct.