A hemispherical tank full of water is emptied by a pipe at the rate of litres per second. How much time will it take to empty the tank, if it is 3 m in diameter? (Take π = )

OR

Two cones with same base diameter 16 cm and height 15 cm are joined together along their bases. Find the surface area of the shape so formed.

Given: Tank is in form of hemisphere with diameter = 3m

To find: Time taken to empty the tank

Proof:

Diameter = 3m

[∵1m³ = 1000 litres]

Now, it is given that

Tank is emptied at litres per second i.e. litres per second

Time taken to empty litres = 1 second

= 990 seconds

= 16.5 minutes

OR

Given: Two cones with same base diameter 16cm and height 15cm

To find: Surface area of shape formed

Proof:

If two cones with same base and height are joined together along their bases, then the shape so formed looks like as figure shown below:

Diameter of cone = 16cm

Height of cone, h = 15cm

So, the surface area of the shape so formed

= CSA of first cone + CSA of second cone

Since both cones are identical,

∴ the surface area of the shape = 2 × CSA of the cone

We know that,

Curved Surface Area of Cone = πrl

= 2 × πrl

= 854.85 cm²

= 855 cm² (approx.)

Hence, the surface area of shape is 855 cm²