Question

A boy on 20 minutes at a uniform speed of 18 kilometre per hour at what speed should he ran for the next day 40 minutes so that the average speed kam 24 km per hour ​

Answer 1

Provided:-

• The boy travelled with uniform speed of 18 km/hr for 20 minutes.
• And, next he ran for 40 minutes, with a different speed.
• Average speed of the boy = 24 km/hr

To Find:-

• With what speed he travelled for 40 minutes?

How to solve?

While solving the question, we just need to keep a relation in mind I.e. the relation between average speed, Distance and time. The relation is:

$\large{ \boxed{ \sf{avg. \: speed = \frac{total \: distance}{total \: time}}} }$

☃️ So, Let's solve this question...

Solution:-

With speed = 18 km/hr,

• Time travelled = 20 mins = 1/3 hr

Then, Distance travelled,

➝ Distance = Speed × Time

➝ Distance = 18 km/hr × 1/3 hr

➝ Distance = 6 km

With speed 2),

• Time travelled = 40 mins = 2/3 hr
• Let the distance travelled be x

So,

• Then, Total dis. travelled = 6 + x km
• Total time taken = 1/3 hr + 2/3 hr = 1 hr

Given,

• Average speed = 24 km/hr

➝ (6 + x ) km / 1 hr = 24 km/hr

➝ (6 + x) km/hr = 24 km/hr

➝ x = 24 - 6 km

➝ x = 18 km

✒ Distance travelled in 40 mins = 18 km

Now,

• Distance travelled = 18 km
• Time taken = 40 mins = 2/3 hr

Finding speed,

➝ Speed = Distance/Time

➝ Speed = 18 km/ 2/3 hr

➝ Speed = 27 km/hr

☀️ Speed of the body in that 40 minutes duration = 27 km/hr.

━━━━━━━━━━━━━━━━━━━━