In the diagram shown, 21 identical metallic balls were placed between two walls with equally spaced gaps between them. The first metallic ball and the last metallic ball were touching the front wall and last wall respectively. Given that the distance between the two walls was 445 cm and that the radius of a metallic ball was 7 cm. Find the length of the gap between any two adjacent metallic balls as shown.
Diameter of the metallic ball
= 7 x 2 
= 14 cm

Distance covered by 21 balls
= 21 x 14
= 294 cm

Distance left for the gaps
= 445 - 294
= 151 cm

Total number of gaps between the balls
= 21 - 1
= 20

Length of the gap between two balls
= 151 ÷ 20
= 7.55 cm

Answer(s): 7.55 cm