See image attached
We could find the length of the radius of the small circle using pythagorean theorem. There is a right triangle formed from the picture above. Pythagorean theorem states the sum of the squares of the perpendicular sides on the right triangle is equal to the square of its hypotenuse.
(8 - r)² + 20² = 21²
(8 - r)² + 400 = 441
(8 - r)² = 441 - 400
(8 - r)² = 41
8 - r = √41
r = 8 - √41
r = 8 - 6.403
r = 1.597
to the nearest tenth
r ≈ 1.6
The radius of the small circle is approximately 1.6 in
