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14710.53.5

Answer :

ASolution :

Let the radii of the circles be denoted by `r_(1)` cm and `r_(2)` cm where `r_(1) ge r_(2)`. As the circles touch each other externally, distance between their centres = Sum of their radii. <br> ` :. R_(1)+r_(2)=28 " (1)" ` <br> Also `pi(r_(1))^(2)+pi(r_(2))^(2)=490 pi` <br> ` :. (r_(1))^(2)+(r_(2))^(2)=490 " (2)" ` <br> Squaring both sides of Eq. (1), we get <br> `(r_(1))^(2)+(r_(2))^(2) + 2(r_(1))(r_(2))=784` <br> `r_(1)*r_(2)=147 " (3)" ` <br> Solving Eqs. (1) and (3), we get <br> `r_(1)=21 and r_(2) =7. ( :. r_(1) ge r_(2))` <br> ` :. ` Required difference = 14 cm.**Review from previous class**

**Cuboid**

**Cube**

**Right Circular Cylinder**

**Right Circular hollow cylinder**

**Right Circular Cone**

**Sphere and Hemisphere**

**Spherical Shell**

**Conversion of cube into cuboid by Joining : Two cubes each of 10 cm edge are joined end to end. Find the surface area and volume of cuboid.**

**Conversion of cubes by Melting and Recasting : Three cubes are melted, whose edges are `3 cm, 4 cm and 5 cm` to form a single cube. Find its edge; volume and surface area.**