The distance from the earth to the moon is 2.4 x 10 5 mi. Light (and radiowaves) travel at 3.0 x 10 10 cm/sec. How long does it take for a radio signal to reach the moon?

Answer 1

Using dimensional analysis:

2.4x10⁵ miles x 5280 feet/mile x 12 inches/ft x 2.54 cm/inch x 1 sec/3.0x10¹⁰ cm = 1.28 seconds = 1.3 sec