A box is 1 m long, 60 cm wide and 40 cm high. Find the expenditure of colouring its all outer side without its bottom at the rate of Rs.20 per square meter.
Length of box (l)=1m
Breadth of box (b)=60cm=0.6m
Height of box (h)=40cm=0.4m
Area of box =2(lb+bh+hl)=2(1×0.6+0.6×0.4+0.4×1)=2×(0.6+0.4+0.24)=2×1.24=2.48m2Area of bottom =l×b=1×0.6=0.6m2
Therefore,
Cost of colouring per square meter =Rs.20
Total expenditure of colouring its all outer side without its bottom =20×(2.48−0.6)=2×1.88=Rs.3.76