ABC is a triangle with AB = 10 cm, BC = 8 cm and AC = 6cm (not drawn to scale). Three circles are drawn touching each other with the vertices as their centers. Find the radii of the three circles.
ABC is a triangle with AB = 10 cm, BC = 8 cm and AC = 6cm (not drawn to scale). Three circles are drawn touching each other with the vertices as their centers. Find the radii of the three circles.

Selina Solutions Concise Class 10 Maths Chapter 18 ex. 18(C) - 22

Solution:

According to the given question,

ABC is a triangle with \[AB\text{ }=\text{ }10\text{ }cm,\text{ }BC=\text{ }8\text{ }cm,\text{ }AC\text{ }=\text{ }6\text{ }cm\]

Three circles are drawn with centre \[A,\text{ }B\text{ }and\text{ }C\]touch each other at \[P,\text{ }Q\text{ }and\text{ }R\] respectively.

So, we need to find the radii of the three circles.

Let,

\[PA\text{ }=\text{ }AQ\text{ }=\text{ }x\]

\[QC\text{ }=\text{ }CR\text{ }=\text{ }y\]

\[RB\text{ }=\text{ }BP\text{ }=\text{ }z\]

So, we have

\[x\text{ }+\text{ }z\text{ }=\text{ }10\text{ }\ldots ..\text{ }\left( i \right)\]

\[z\text{ }+\text{ }y\text{ }=\text{ }8\text{ }\ldots \ldots \text{ }\left( ii \right)\]

\[y\text{ }+\text{ }x\text{ }=\text{ }6\text{ }\ldots \ldots .\text{ }\left( iii \right)\]

Adding all the three equations, we have

\[2\left( x\text{ }+\text{ }y\text{ }+\text{ }z \right)\text{ }=\text{ }24\]

\[x\text{ }+\text{ }y\text{ }+\text{ }z\text{ }=\text{ }24/2\text{ }=\text{ }12\text{ }\ldots ..\text{ }\left( iv \right)\]

Subtracting (i), (ii) and (iii) from (iv) we get

\[y\text{ }=\text{ }12\text{ }-\text{ }10\text{ }=\text{ }2\]

\[x\text{ }=\text{ }12\text{ }-\text{ }8\text{ }=\text{ }4\]

And,

\[z\text{ }=\text{ }12\text{ }-\text{ }6\text{ }=\text{ }6\]

Thus, radii of the three circles are \[2\text{ }cm,\text{ }4\text{ }cm\text{ }and\text{ }6\text{ }cm\]