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Basic Formula & Direct Conversion

Introduction

हर Time, Speed और Distance problem एक बहुत simple लेकिन powerful relationship से शुरू होती है। यह foundation समझ लेने से आप किसी भी motion, travel या speed से जुड़े सवाल - चाहे car journey हो, train हो या कोई व्यक्ति चल रहा हो - आसानी से solve कर सकते हैं।

यह pattern आपकी basic foundation बनाता है ताकि जब तीन में से कोई दो values (distance, speed, time) दी हों, तो तीसरी जल्दी निकाली जा सके।

Pattern: Basic Formula & Direct Conversion

Pattern

मुख्य formula है: Speed = Distance ÷ Time

इसी से बाकी दो formulas सीधे बनते हैं:

  • Distance = Speed × Time
  • Time = Distance ÷ Speed

ध्यान रखें: Units हमेशा consistent होने चाहिए - अगर distance km में है, तो time hours में और speed km/h में होगी; अगर distance meters में है, तो time seconds में और speed m/s में होगी।

Step-by-Step Example

Question

एक car 150 km को 3 hours में तय करती है। उसकी speed निकालें।

Solution

  1. Step 1: Given Values पहचानें

    Distance = 150 km, Time = 3 hours.
  2. Step 2: Formula लगाएं

    Speed = Distance ÷ Time
  3. Step 3: Substitute और calculate करें

    Speed = 150 ÷ 3 = 50 km/h.
  4. Final Answer:

    Car की speed = 50 km/h.
  5. Quick Check:

    अगर car 50 km/h की speed से 3 hours चले → Distance = 50 × 3 = 150 km ✔️ (Correct!)

Quick Variations

1. Speed और time दिए हों → Distance निकालें।

2. Distance और speed दिए हों → Time निकालें।

3. Direct unit conversion (जैसे km/h से m/s)।

4. Comparative travel problems - अलग-अलग cases पर यही formula apply करें।

Trick to Always Use

  • Step 1: Base formula लिखें (S = D ÷ T).
  • Step 2: Values लगाने से पहले units check करके same units में convert करें।
  • Step 3: “Triangle Formula” याद रखें (ऊपर D, नीचे S और T)।
  • Step 4: Answer को D = S × T से verify करें।

Summary

Summary

  • याद रखने वाला formula: S = D ÷ T.
  • Rearranged forms: D = S × T और T = D ÷ S.
  • Units हमेशा consistent रखें (km-km/h-hr या m-m/s-s).
  • Opposite formula लगाकर answer को cross-check ज़रूर करें।

Practice

(1/5)
1. A cyclist covers 60 km in 4 hours. Find his speed.
easy
A. 15 km/h
B. 12 km/h
C. 20 km/h
D. 18 km/h

Solution

  1. Step 1: Identify Given Values

    Distance = 60 km, Time = 4 hours.
  2. Step 2: Apply Formula

    Speed = Distance ÷ Time.
  3. Step 3: Substitute and Calculate

    Speed = 60 ÷ 4 = 15 km/h.
  4. Final Answer:

    Speed = 15 km/h → Option A.
  5. Quick Check:

    15 × 4 = 60 ✅
Hint: Speed = Distance ÷ Time - divide distance by time directly.
Common Mistakes: Forgetting to divide correctly or mixing up units.
2. A car runs at a speed of 60 km/h for 2 hours. How much distance does it cover?
easy
A. 100 km
B. 110 km
C. 120 km
D. 150 km

Solution

  1. Step 1: Identify Given Values

    Speed = 60 km/h, Time = 2 hours.
  2. Step 2: Apply Formula

    Distance = Speed × Time.
  3. Step 3: Substitute and Calculate

    Distance = 60 × 2 = 120 km.
  4. Final Answer:

    Distance = 120 km → Option C.
  5. Quick Check:

    120 ÷ 2 = 60 km/h ✅
Hint: Multiply speed and time directly to find distance.
Common Mistakes: Dividing instead of multiplying.
3. A train covers 240 km at a uniform speed of 80 km/h. Find the time taken.
easy
A. 2 hours
B. 3 hours
C. 4 hours
D. 5 hours

Solution

  1. Step 1: Identify Given Values

    Distance = 240 km, Speed = 80 km/h.
  2. Step 2: Apply Formula

    Time = Distance ÷ Speed.
  3. Step 3: Substitute and Calculate

    Time = 240 ÷ 80 = 3 hours.
  4. Final Answer:

    Time taken = 3 hours → Option B.
  5. Quick Check:

    80 × 3 = 240 ✅
Hint: Use Time = Distance ÷ Speed when speed is given.
Common Mistakes: Reversing formula as Speed ÷ Distance.
4. A person walks at 5 km/h for 2 hours and then runs at 10 km/h for 1 hour. Find total distance covered.
medium
A. 15 km
B. 25 km
C. 30 km
D. 20 km

Solution

  1. Step 1: Split Movements

    First part: 5 km/h × 2 h = 10 km. Second part: 10 km/h × 1 h = 10 km.
  2. Step 2: Add Distances

    Total Distance = 10 + 10 = 20 km.
  3. Final Answer:

    Total distance = 20 km → Option D.
  4. Quick Check:

    Average speed = 20 ÷ 3 ≈ 6.67 km/h (logical) ✅
Hint: Break the journey into parts and sum distances.
Common Mistakes: Adding speeds instead of distances.
5. A bus travels 90 km at 45 km/h and returns the same distance at 30 km/h. Find the total time taken for the trip.
medium
A. 5 hours
B. 3 hours
C. 4 hours
D. 6 hours

Solution

  1. Step 1: Identify Given Values

    Onward: 90 km at 45 km/h; Return: 90 km at 30 km/h.
  2. Step 2: Find Time for Each Part

    Onward time = 90 ÷ 45 = 2 h; Return time = 90 ÷ 30 = 3 h.
  3. Step 3: Add Total Time

    Total time = 2 + 3 = 5 hours.
  4. Final Answer:

    Total time = 5 hours → Option A.
  5. Quick Check:

    Total distance = 180 km, average speed = (2×45 + 3×30) / 5 = 36 km/h ⇒ 180 ÷ 36 = 5 h ✅
Hint: Calculate each leg separately using Time = Distance ÷ Speed.
Common Mistakes: Averaging speeds instead of using time formula.

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