Finding average speed or rate | Ratios, proportions, units, and rates | Pre-Algebra | Khan Academy

TL;DR

Usain Bolt's average speed during a 100-meter race was calculated to be 23.3 miles per hour.

Transcript

SALMAN KHAN: I have some footage here of one of the most exciting moments in sports history. And to make it even more exciting, the commentator is speaking in German. And I'm assuming that this is OK under fair use, because I'm really using it for a math problem. But I want you to watch this video, and then I'll ask you a question about it. [CHEERI... Read More

Key Insights

• 🐎 Usain Bolt's average speed during the 100-meter race was calculated to be 23.3 miles per hour.
• ☠️ Salman Khan used the formula Distance = Rate × Time to calculate Bolt's average speed.
• 🙃 Khan divided both sides of the equation by 9.58 seconds to isolate the rate variable and solve for it.

Questions & Answers

Q: How did Salman Khan calculate Usain Bolt's average speed during the 100-meter race?

Salman Khan used the formula Distance = Rate × Time to calculate Bolt's average speed. By plugging in the known values of 100 meters for distance and 9.58 seconds for time, Khan solved for the rate variable.

Q: Why did Salman Khan divide both sides of the equation by 9.58 seconds?

Khan divided both sides of the equation by 9.58 seconds to isolate the rate variable, which was the value he wanted to solve for. Dividing both sides of an equation by the same value ensures that the equality remains true.

Q: What units did Salman Khan express Bolt's average speed in initially?

Salman Khan initially expressed Bolt's average speed in meters per second.

Q: How did Salman Khan convert Bolt's average speed from meters per second to kilometers per hour?

To convert Bolt's average speed from meters per second to kilometers per hour, Khan divided Bolt's average speed by 1,000 (since there are 1,000 meters in one kilometer) and then multiplied it by 3,600 (since there are 3,600 seconds in one hour).

Summary & Key Takeaways

• Salman Khan presents a video of Usain Bolt's record-breaking 100-meter race.

• Khan poses the question of calculating Bolt's average speed during the race.

• By using the formula Distance = Rate × Time, Khan guides viewers through the calculation process.

• The resulting calculation reveals that Bolt's average speed was 23.3 miles per hour.