In this when we again make a cylinder which is folded along breadth then the radius calculated is wrong.
2 pi r = 3/2x

“ Question no.12

The length and breadth of a rectangle are in the ratio 4 : 3. The rectangle is folded along the length to form a cylinder and then the cylinder is cut into half horizontally. The cylinder is then opened again to form a rectangle which is again folded along the breadth to form another cylinder. Find the ratio of the radius and the height of the cylinder thus formed.

A 4π:3

B 16π:3

C 8π:3

D None of these

Explanation

ANSWER - D

Let the length of the rectangle be and the breadth of the rectangle is.

Cutting the cylinder into half and then opening it again will give us a rectangle with length  and breadth 

Now, the rectangle is folded again to form a cylinder of height '  ' 

And the radius of the cylinder '  ' 

 The ratio of the height and radius of the cylinder is 

Therefore (d) “