You are planning to make an open rectangular box from a 24-in.-by-47-in. piece of cardboard by cutting congruent squares from
the corners and folding up the sides. What are the dimensions of the box of largest volume you can make this way, and what is its volume?
1 answer:
Answer:
The dimensions are 13.92inches by 36.92inches by 5.04inches
Volume is 2590.18 inches³
Step-by-step explanation:
see attachment for the figure
supposing 'h' is side length of the square and also the height of the box
then, According to the question
Length of the box 'L'= 47 - 2h
Width of the box 'w'= 24 - 2h
Volume of the box 'V'= hLw
Substituting the values of 'L' and 'w' in above equation
V= h(47 - 2h)(24 - 2h)
V=(47h - 2h²)(24 - 2h) => 1128h - 94h²-48h²+4h³
V= 4h³ -142h²+1128h -->eq(1)
Taking derivative on both sides.
V' = 12h² - 284h + 1128
Setting the equation to zero, we will have
0=12h² - 284h + 1128
0= 3h² - 71h + 282
Using Quadratic formula to find h
h= (-b+-√b²-4ac) / 2a
= 71+-√71² - (4 x 3 x 282) / (2 x 3)=> 71+-√5041- 3384 / 6
h =(71+- 40.706)/ 6
EITHER h= 18.6
OR h=5.04
By substituting the value of 'h' in eq(1)
(1)=>V(18.6)= 4(18.6)³ -142(18.6)²+1128(18.6) => -2406.096
(1)=>V(5.04)= 4(5.04)³ -142(5.04)²+1128(5.04) => 2590.18
By ignoring the negative value, we will have h=5.04
Therefore,
L= 47 - 2h => 47 -2(5.04) =>36.92
w= 24 - 2h=> 24- 2(5.04)=> 13.92
The dimensions are 13.92inches x 36.92inches x 5.04inches
Volume is 2590.18 inches³
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