Calculate the Increased Speed: Caterpillar's Journey from 3 cm/min to ?

Average Speed Problems with Two-Phase Motion

A caterpillar crawls for two minutes at a speed of 3 cm per minute, then increases its speed and continues crawling.

In total, the caterpillar advances 30 cm and its average speed is 4.412 cm per minute.

How fast does it travel after increasing its speed?

❤️ Continue Your Math Journey!

We have hundreds of course questions with personalized recommendations + Account 100% premium

Step-by-step video solution

Watch the teacher solve the problem with clear explanations

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

A caterpillar crawls for two minutes at a speed of 3 cm per minute, then increases its speed and continues crawling.

In total, the caterpillar advances 30 cm and its average speed is 4.412 cm per minute.

How fast does it travel after increasing its speed?

2

Step-by-step solution

To solve this problem, we'll proceed as follows:

Let us begin by calculating the distance covered in the initial phase of the journey:

  • Since the caterpillar crawls for 2 minutes at 3 cm per minute, the distance D1 D_1 covered is: D1=3×2=6 D_1 = 3 \times 2 = 6 cm.

Given that the total distance traveled by the caterpillar is 30 cm, the distance covered after increasing its speed, D2 D_2 , is:

  • D2=306=24 D_2 = 30 - 6 = 24 cm.

Next, we use the average speed to determine the total time of the entire journey. The average speed formula is given by:

  • Vˉ=Total distanceTotal time\bar{V} = \frac{\text{Total distance}}{\text{Total time}}
  • Thus, the total time T T is: T=304.4126.8 T = \frac{30}{4.412} \approx 6.8 minutes.

The time taken at the increased speed (t2 t_2 ) is then t2=Tt1=6.82=4.8 t_2 = T - t_1 = 6.8 - 2 = 4.8 minutes.

Finally, to find the increased speed V2 V_2 , we use the relationship:

  • V2=D2t2=244.8=5 V_2 = \frac{D_2}{t_2} = \frac{24}{4.8} = 5 cm per minute.

Therefore, the caterpillar travels at 5 cm per minute after increasing its speed.

3

Final Answer

5 5 cm per minute

Key Points to Remember

Essential concepts to master this topic
  • Formula: Average speed equals total distance divided by total time
  • Technique: Find remaining distance: 30 - 6 = 24 cm
  • Check: Verify total time: 6.8 minutes gives average 30/6.8 ≈ 4.412 cm/min ✓

Common Mistakes

Avoid these frequent errors
  • Using average speed formula incorrectly for second phase
    Don't calculate the second speed as (total distance - first distance) ÷ first time = wrong speed! This ignores that the caterpillar spent different times in each phase. Always find the actual time for each phase: total time minus first phase time.

Practice Quiz

Test your knowledge with interactive questions

What is the average speed according to the data?

TravelTimekm/hDistance3122.570400100210400250

FAQ

Everything you need to know about this question

Why can't I just subtract the first speed from the average speed?

+

Because average speed isn't a simple arithmetic mean of the two speeds! It depends on both distance and time. The caterpillar could spend different amounts of time at each speed, making this approach incorrect.

How do I find the total time if I only know the average speed?

+

Use the formula: Total time=Total distanceAverage speed \text{Total time} = \frac{\text{Total distance}}{\text{Average speed}} . In this problem: T=304.4126.8 T = \frac{30}{4.412} \approx 6.8 minutes.

What if the average speed calculation gives me a decimal?

+

That's normal! Real-world problems often have decimal values. Just be careful with rounding - keep enough decimal places during calculations and round only your final answer.

Can I check my answer another way?

+

Yes! Calculate the weighted average: 3×2+5×4.82+4.8=306.84.412 \frac{3 \times 2 + 5 \times 4.8}{2 + 4.8} = \frac{30}{6.8} \approx 4.412 cm/min. This should match the given average speed.

What if I get a negative time for the second phase?

+

This means there's an error in your calculation! Check that the total distance and average speed are reasonable. The caterpillar must have spent enough time to cover the remaining distance.

🌟 Unlock Your Math Potential

Get unlimited access to all 18 Traffic Flow Problems questions, detailed video solutions, and personalized progress tracking.

📹

Unlimited Video Solutions

Step-by-step explanations for every problem

📊

Progress Analytics

Track your mastery across all topics

🚫

Ad-Free Learning

Focus on math without distractions

No credit card required • Cancel anytime

More Questions

Click on any question to see the complete solution with step-by-step explanations