Question

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?

Answer 1

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