Medium
The distance between the Sun and the Earth is about 1.5 × 10⁸ km and the speed of light is 3 × 10⁸ m/s. How long does sunlight take to reach the Earth?
Explanation
Explanation
Step 1: Convert the distance to metres: 1.5 × 10⁸ km = 1.5 × 10⁸ × 1000 m = 1.5 × 10¹¹ m.
Step 2: Time = distance ÷ speed = (1.5 × 10¹¹) ÷ (3 × 10⁸) = 0.5 × 10³ = 500 s.
Step 3: Convert: 500 s = 8 minutes + 20 seconds (since 8 × 60 = 480).
Answer: 8 minutes 20 seconds.
PRO TIP
Re-check your working by substituting the answer back into the original question.