Question

A truck covers 30km at a uniform speed of 30km/h .Whta should be it's for the next 90km if the average speed for the entire journey is 60km/h..

Answer 1

$\large\bf\underline{Given:-}$

• A truck covers 30km at a uniform speed of 30km/h.

$\large\bf\underline {To \: find:-}$

• we need to find the speed of the truck for the next 90km if the average speed for the entire journey is 60km/h.

$\huge\bf\underline{Solution:-}$

• Distance travelled by truck = 30km
• Speed of truck = 30km/hr

▶️ According to Question :--

If the truck have to travel for the next 90km.

then average speed for entire journey = 60km/hr

we know that,

$\bf \mid \overline {\underline{Average \: speed = \frac{total \: distance \: covered}{total \: time \:taken} }} \mid$

• Average speed = 60km/hr
• total distance = 90 + 30
• total distance = 120km

now substituting these values in formula

↣60km/hr = 120/Total time

↣Total time = 120/60

↣Total time = 2hr

So, the truck will cover the entire journey in 2hours.

It is already given in the question that the truck travelled 30km with the speed of 30km/hr

So,

Speed = distance/time

≫ 30 = 30/time

≫ time = 30/30

≫ time = 1hr

So, the truck will cover 30km distance with the speed of 30km/hr in 1 hour.

Now calculating Speed of truck when it will cover next 90km

• Time = 1hr
• distance = 90km

Speed = distance/time

↣speed = 90/1

↣speed = 90km/hr

hence

For the next 90km the truck's speed is 90km/hr.

$\rule{200}3$

Answer 2

★ Question

A car covers 30km at a uniform speed of 30km/h . What should be its speed for the next 90 km if the average speed for the entire journey is 60km/h?

$\rule{230}2$

★ Solution

Given: total distance= 120 km

★ Avg. Speed = 60 km/h

★ Time taken by car to cover 30 km= 30/30= 1 hr

★ Let the speed of car for next 90km be x

So,

★ the time taken to complete 90 km = 90/x

Now,

★ Avg. Speed = total distance/ total time taken

→ 60 = 120/(1+(90/x))

→ 60(x+90)= 120x

→ 60x + 5400 = 120x

→ 60x = 5400

→ x = 90 km/h (speed for next 90 km)