RRB RPF RPSF SI and CONS Model Papers 9 with solutions

Question : 57 of 120

Marks: +1, -0

If the circumference and area of a circle are numerically equal, then the diameter is equal to :

Solution:

(4) We know that The area of circle

=\π r^{2}

= {\πD^{2}}/{4}

[where D : Diameter of circle)
and Circumference of circle

=2 \π^{2} {r}=\π{D}

Now, according to question,

{\π D^{2}}/{4}=\π D

{D}^{2}=4 {D}

{D}^{2}-4 {D}=0

or,

{D}( {D}-4)=0

or,

{D}=4

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