Question

speed,distances and time pls help question number 9 and 10​

Answer 1

Solution -

We know that

Distance = Speed × Time

Speed = $\sf\dfrac{distance}{time}$

Also , Time = $\sf\dfrac{distance}{speed}$

9. In the Question it is given that ,

$\sf{Distance_1}$ = 160 km

$\sf{Distance_2}$ = 180 km

$\sf{Distance_3}$ = 200 km

$\sf{Speed_1}$ = 40 km / h

$\sf{Speed_2}$ = 45 km / h

$\sf{Speed_3}$ = 50 km / h

So , therefore time taken to cover 160 km

= $\sf\dfrac{160}{40}$

= 4 hours

Time taken to cover 180 km

= $\sf\dfrac{180}{45}$

= 4 hours

Time taken to cover 200 km

= $\sf\dfrac{200}{50}$

= 4 hours

Total time taken = 4 + 4 + 4 = 12 hours

Average speed = $\sf\dfrac{40\:+\:45\:+\:50}{3}$

= 45 km / h

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10. Total distance covered by the train = 670 km

Tim taken to cover 670 km = 6 hr 5 min or $\sf\dfrac{73}{12}$

Speed during covering 390 km was 90 km / h

Time taken to cover 390 km = $\sf\dfrac{390}{90}$

= $\sf\dfrac{13}{3}\: hours$

Remaining distance = 670 - 390 = 280 km

To find the speed we need to find the time first so let's calculate the remaining time to complete rest of the journey

$\sf{=\:\dfrac{73}{12}\:-\:\dfrac{13}{3}}$

$\sf{=\:\dfrac{73}{12}\:-\:\dfrac{52}{12}}$

$\sf{=\:\dfrac{21}{12}\:=\:\dfrac{7}{4}\:hours}$

Speed for rest of the journey = $\sf\dfrac{280}{\frac{7}{4}}$

= $\sf\dfrac{280\:\times\:4}{7}$

= $\sf\dfrac{1120}{7}$

= 160 km / h

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ii ) Total distance covered by bus = 630 km

Time taken to cover 630 km = 9 hours

Two third of journey = $\sf\dfrac{2}{3}\:\times\:630$

= 420 km

Speed for 420 km = 60 km / h

Time taken to cover 420 km = $\sf\dfrac{distance}{speed}$

= $\sf\dfrac{420}{60}$

= 7 hours

Remaining distance = 630 - 420 = 210 km

Remaining time to cover 210 km = 9 - 7 = 2 hours

Speed for rest journey = $\sf\dfrac{distance}{time}$

= $\sf\dfrac{210}{2}$ = 105 km / h

Answer 2

Answer:

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