4. Five marks exercise problems - II

1. The radius of a sphere increases by 25\(\%\). Find the percentage increase in its surface area.

 

Answer:

 

Percentage increased in surface area \(=\) \(\%\)

 

[Note: Enter your answer up to two decimal places]

 

 

2. The internal and external diameters of a hollow hemispherical vessel are \(20 \ cm\) and \(28 \ cm\), respectively. Find the cost to paint the vessel all over at \(₹0.14 \) per \(cm^2\).

 

Answer:

 

The cost to paint the vessel \(=\) \(₹\)

 

[Note: Enter your answer up to two decimal places]

 

 

3. The frustum shaped outer portion of the table lamp has to be painted including the top part. Find the total cost of painting the lamp if the cost of painting \(1\) sq.m is \(₹2\).

 

Answer:

 

The total cost of painting the lamp \(=\) \(₹\)

 

[Note: Enter your answer up to one decimal place]