answer:
Total surface area of 3 tanks=34.3 m^2
7 tins of paint are required.
Solution,
diameter of tank=1.4 m
Height of tank=1.9 m
Given tank has top and bottom
Now, The total surface area of cylinder tank is given by:

r( radius of tank)=

h(height of tank)=1.9 m
TSA of 1 tank
=

TSA Of 3 tanks
=

Given a tin of plate covers 5m^2 area.
No.of tins required:
1 tin 5m^2
x tin 34.3 m^2

therefore 7 tins are required.
Hope this helps...
Good luck on your assignment....