Find radius

There are six circles of equal radius and are arranged as an equilateral triangle.
Find the radius of the circle.

13 Answers

62
Lokesh Verma ·

simple:

4R sin 60 + 2R = 4

R = 2/(1+√3) = 2(√3-1)

1
sri 3 ·

Thanks Sir......Never thought about the height of the equilateral triangle in terms of sin
And rahul...Nishant sir's answer is rite.

36
rahul ·

Maybe its 4√3/9 .... not sure and confident as Nishant sir's answer is quite different.

1
nihal raj ·

draw the altitude on this equilateral triangle by drawing radius of these small circles.....

we get two similar triangles...

now apply .....sinA/a = sinB/b = sin C/c

sin30/2r= sin60/4

1/4r=√3/8

2/√3=r

1
venkateshan ·

So R = √3 - 1

check that there is a slight mistake in nishant sir's calculation......

1
nihal raj ·

.....sinA/a = sinB/b = sin C/c

sin30/2r= sin60/4-2r

1/4r=√3/[2(4-2r)]

8-4r=4√3r

8/4√3+4=r

r= 2/√3+1 r= (√3-1)= ans....

@ venketesha ... u have made mistake in calculations dude....

36
rahul ·

The answer must be 2/root(3)

36
rahul ·

1
nihal raj ·

U MADE THE same mistake as i did in my earlier post ... the height is 4-2r and not 4..see the figure carefully.........

1
sri 3 ·

The answer in √3 - 1.........Nishant Sir just made a very small mistake in the last step
And rahu....l......The height of the right angle triangle u have drawn in not 4......
It is 4 - 2r

36
rahul ·

Exactly.... true. true. true......

ya....

36
rahul ·

Maybe this is correct....

1
venkateshan ·

but nihal... whts my mistake.... i too got the ans as √3-1

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