Question

3. State the laws of reflection. 4. A truck covered first 50 km of a journey in 3 hours, next 120 km in 4 hours and last 50 km in 4 hours. Calculate the average speed
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Answer 1

Explanation:

Solution

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As we know that

speed=

time

distance

Time taken by the car t travel 160km when travelling with the speed of 40km/hr=

40

160

=4 hour

Time taken by the car t travel 120km when travelling with the speed of 60km/hr=

60

120

=2 hour

Now,

Total distance travelled by the car =160+120=280km

Total time taken =4+2=6 hours

Therefore,

Average speed =

total time

Total distance

=

6

280

=46.67km/hr

Answer 2

$\large{ \underline{ \underline{ \sf \green{Given:- }}}}$

• A car covers first 50 km in 45 minutes.
• It covered next 50 km in 30 minutes and next 50 km in 1 hour.

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

• The average speed of car

● Using Formula :-

• ${ \boxed{\sf{ \orange {Average\: Speed = \frac{Total \: distance}{Total \: time}}}}}$

$\large{ \underline{ \underline{ \sf \pink{Solution:- }}}}$

Total distance covered by car will be

➣ (50 + 50 + 50) km

➣ 150 km

Now, we have to change the minute into hour

➪ To change minute into hour, we divide by 60. { since , 1 hour = 60 minutes }

• 45 minutes = 45/60 = 3/4 hours
• 30 minutes = 30/60 = 1/2 hours
• 60 minutes = 1 hour
• So, Total time taken by car will be

➣ t¹ + t² + t³

➣ (3/4 + 1/2 + 1) hours

➣ (3 + 2 + 4/4) hours

➣ 9/4 hours

∴ Average Speed of car

$\orange{ \sf\implies{\rm } Average \: Speed = 150/9/4}$

$\sf \orange{\implies{\rm }Average \: Speed = 150(4)/9}$

$\sf \orange{\implies{\rm } Average \: Speed = 600/9}$

$\sf \orange{\implies{\rm } Average \: Speed = 66.666}$

The Average Speed of car is 66.67 km/hr approx.