Question

The sun's light takes about 5.3 hours to reach Pluto. Which of the following is the correct method of finding the distance, in kilometers, between the sun and Pluto?
Divide 5.3 by the time it takes light to reach Earth Multiply 5.3 by the time it takes light to reach Earth Divide 5.3 by the speed of light in kilometers per hour Multiply 5.3 by the speed of light in kilometers per hour

Answer 1

The correct answer is
Multiply 5.3 by the speed of light in kilometers per hour

In fact, the light moves by uniform motion, so we can use the relationship
$v= \frac{S}{t}$
where S is the distance covered by the light, t the time it takes, and v the speed of light.
So, if we want to find the distance between Sun and Pluto,
$S=v t$
which means that we should multiply the time (5.3 hours) by the speed of light in km/h.