Question

A car covers first 100 km of his journey at 50
km/h, next 50 km at 40 km/h and last 75 km
in 14 h.
Find the average speed of the whole
journey.


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Answer 1

$\large\underline{\red{\sf \orange{\bigstar} Given:-}}$

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• A car covers first 100 km of his journey at 50 km/h, next 50 km at 40 km/h and last 75 km in 14 km/h.

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$\large\underline{\pink{\sf \red{\bigstar} To Find:-}}$

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• Average speed of whole journey

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$\large\underline{\blue{\sf \orange{\bigstar} Solution:-}}$

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⭐In first case

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A car covers first 100 km of his journey at 50 km/h

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• Distance (D1) = 100km
• Speed = 50 km/h

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As we know that

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• → Time = distance/speed

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• → T1 = 100/50

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• → T1 = 2 hours

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⭐In second case

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• A car covers 50 km of his journey at 40 km/h

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• D2 = 50km

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• Speed = 40km/h

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• → Time = distance/speed

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• → T2 = 50/40

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• → T2 = 5/4

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• → T2 = 1.25 hours

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⭐In third case

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A car covers 75 km of his journey at 14 km/h

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• D3 = 75km

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• Speed = 14km/h

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• → T3 = 75/14

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• → T3 = 5.35 hours

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$\large\underline{\purple{\sf \orange{\bigstar} Now:-}}$

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• → Average speed = Total distance travelled/total time

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• → Average speed = D1 + D2 + D3/T1 + T2 + T3

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• → Average speed = 100 + 50 + 75/2 + 1.25 + 5.35

• → Average speed = 225/8.6

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• → Average speed = 26.16 km/h

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$\large\underline{\green{\sf \pink{\bigstar} Hence:-}}$

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$\large\underline{\red{\sf \orange{\bigstar} • Average\:\:speed \:\:of \:\:a \:\:car\:\: is\:\: 26.16\:\:km/h}}$

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Answer 2

✦Given-

A car covers it's first 100 km of  journey at 50 km/h, next 50 km at 40 km/h and last 75 km in 14 km/h.

✦To find-⠀⠀⠀⠀⠀⠀⠀

Average speed of whole journey.

⚫In the 1st case-

The car covers first 100 km of it's journey at 50 km/h

Distance (D1) = 100km

Speed = 50 km/h

Time = distance/speed

➻ T1 = 100/50

➻ T1 = 2 hours

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⚫In the 2nd case-

The car covers 50 km of it's journey at 40 km/h.

D2 = 50km

Speed = 40km/h

Time = distance/speed

➻ T2 = 50/40

➻ T2 = 5/4

➻ T2 = 1.25 hours

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⚫In the 3rd case-

The car covers 75 km of it's journey at 14 km/h

D3 = 75km

Speed = 14km/h

➻ Time=distance/speed

➻ T3 = 75/14

➻ T3 = 5.35 hours

Now,

➻ Average speed = Total distance travelled/total time

➻  D1 + D2 + D3/T1 + T2 + T3

➻  100 + 50 + 75/2 + 1.25 + 5.35

➻  225/8.6

➻ Average speed = 26.16 km/h

∴ The average speed of the whole journey is 26.16 Km/h.

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