1.

The radius of a circular card board is 20 cm. A strip of width 4 cm is removed all along its border. The percenrage of the area of the strip removed is _______.A. `50%`B. `36%`C. `40%`D. `25%`

Answer» Correct Answer - B
`"Area of the strip removed"=pi(20^(2)-16^(2))`
`=pi(400-256)=144pim^(2)`
`"Area of the circular card board "=pixx20xx20=400`
`therefore "The required percentage"=(144pi)/(400pi)xx100%`


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