Question

A car travels at a speed of 50km/h for 30min , at 30km/h for the next 15min and then

at 70km/h for next 45min what is the average speed of car?​

Answer 1

Given :

First case :-

• Speed of the car = 50 km/hr
• Time = 30 minutes

Second case :-

• Speed of the car = 30 km/hr
• Time = 15 minutes

Third case :-

• Speed of the car = 70 km/hr
• Time = 45 minutes

To find :

• Average speed of the car

Concept :

Firstly, calculate the distance travelled by the car in each case. Then after getting the value of distance in all the cases use the formula to calculate the average speed. The resultant value will our required answer.

Distance is the path travelled by an object.

Mathematically,

Formula to calculate distance :-

• Distance = Speed × Time

Average speed is the total distance travelled by a body divided by the total time taken.

Mathematically,

Formula to calculate average speed :-

• Average speed = Total distance travelled ÷ Total time taken

Solution :

First case →

Firstly, convert the time from minutes in hours.

As we know,

• 1 minute = 1/60 hr

Divide the value by 69 to convert it from minutes into hours.

→ Time = 30/60

→ Time = 3/6

→ Time = 1/2

• Time = 1/2 hrs

Distance travelled by the car in the first case :-

➪ Distance = Speed × Time

Substituting the given values,

➪ Distance = 50 × 1/2

➪ Distance = 25

• Distance travelled by the car in first 30 minutes = 25 km

Second case →

Time = 15 minutes

• 1 min = 1/60 hr

→ Time = 15/60

→ Time = 5/20

• Time = 5/20 hrs

Distance travelled by the car in the second case :-

➪ Distance = Speed × Time

Substituting the given values,

➪ Distance = 30 × 5/20

➪ Distance = 3 × 5/2

➪ Distance = 15/2

➪ Distance = 7.5

• Distance travelled by the car in next 15 minutes = 7.5 km

Third case →

→ Time = 45 minutes

→ Time = 45/60

→ Time = 9/12

→ Time = 3/4

• Time = 3/4 hrs

Distance travelled by the car in the third case :-

➪ Distance = Speed × Time

Substituting the given values,

➪ Distance = 70 × 3/4

➪ Distance = 35 × 3/2

➪ Distance = 105/2

➪ Distance = 52.5

• Distance travelled by the car in next 45 minutes = 52.5 km

Now, calculating the average speed :-

Average speed = Total distance travelled ÷ Total time taken

→ Total distance travelled = 25 + 7.5 + 52.5

→ Total distance travelled = 85

• Total distance travelled by the car = 85 km

→ Total time taken = 1/2 + 5/20 + 3/4

→ Total time taken = 1/2 + 1/4 + 3/4

→ Total time taken = (2 + 1 + 3)/4

→ Total time taken = 6/4

→ Total time taken = 3/2 = 1.5

• Total time taken = 1.5 hrs

We have,

• Total distance = 85 km
• Total time = 1.5 hrs

Substitute the values in the formula of average speed :-

➪ Average speed = 85/1.5

➪ Average speed = 56.67

Therefore,

• The average speed of car = 56.67 km/hr

Answer 2

Answer:

A car travels at a speed of 50 km/h for 30 minutes : Given : Speed = 50 km/h. Time = 30 minutes = 30/60 = 0.5 hours

Step-by-step explanation:

i hope you understand better