3. Fig. 1 shows a square sheet of metal of side 40 cm.
A square x cm by x cm is cut from each corner.
The sides are then bent upwards to form an open box as shown in Fig. 2.
Find the value of x that maximises the volume of the box.
4
02 Bun
Fig. 1
x cm
A
14
x cm
v
Fig. 2
xcm