Answer:
C
Step-by-step explanation:
Calculate AC using Pythagoras' identity in ΔABC
AC² = 20² - 12² = 400 - 144 = 256, hence
AC = = 16
Now find AD² from ΔACD and ΔABD
ΔACD → AD² = 16² - (20 - x)² = 256 - 400 + 40x - x²
ΔABD → AD² = 12² - x² = 144 - x²
Equate both equations for AD², hence
256 - 400 + 40x - x² = 144 - x²
-144 + 40x - x² = 144 - x² ( add x² to both sides )
- 144 + 40x = 144 ( add 144 to both sides )
40x = 288 ( divide both sides by 40 )
x = 7.2 → C
Answer:
x=4 Inch
Step-by-step explanation:
Length of the Square = 24 Inches
If a Square of Length x cm is cut out from each corner
Length of the Box = 24-x-x=(24-2x) Inches
Width of the Box =24-x-x=(24-2x) Inches
Height of the box = x inches
Volume of a Cuboid = Length X Width X Height
V(x)= x(24-2x)(24-2x)
Simplifying
V(x)=4x(12-x)(12-x)
To determine the value of x at which V is largest, we take the derivative of V(x) and solve for the critical points.
V(x)=4x(12-x)(12-x)
Set the derivative equal to zero to obtain the critical points
x cannot be equal to 12 as it divides the length of the square cardboard into exactly two equal parts.
When x=4
V(4)=4*4(12-4)(12-4)=16*8*8=1024 Cubic Inches
When x=4 Inch, the volume, V of the open box is largest.
