Question

25.A 35 cm long metal pipe has external and internal diameter respectively as 12 cm and 10 cm. Find (i) The weight of the metal used if the metal weighs 10 gm per cm 3 . (ii) Cost of painting the pipe on the outside at the rate of Rs. 3 per 100 cm 2

Answer 1

Step-by-step explanation:

In case of a hollow cylinder, the volume is pi*h(R^2-r^2)

[where R is the greater radius]

R= 6 cm

r= 5 cm

h=35

Volume of the cylinder= 22/7*35(36-25)

=22/7*35(9)

=22*5*9

=990 cm cube

So the weight is 990*10

=9900 grams

Now calculating the outer surface area;

CSA=2*22/7*R*h

= 2*22/7*6*35

= 1320 cm square

Therefore rate= 1320/100*3

=13.2*3

39.6 Rupees