The effective length of the first magnet is two times that of the second magnet. The effective length of the third magnet is one-third of the first magnet. If the effectiv length of the second magnet is 7.5 cm, the effective length of the third magnet is ______

Options

A. 5 cm
B. 15 cm
C. 2.5 cm
D. 7.5 cm

Answer

A

Explanation

Effective length of second magnet = 7.5 cm.
Therefore, effective length of the first magnet = 2 x 7.5 = 15 cm
Therefore, effective length of the third magnet = 1/3 x 15 cm = 5 cm.
Hence, the correct option is (a).