Question

A student goes from his home to school 4.0 km away with speed 8.0 km/h, stay in school for 3.5 h and returns back to home with speed 4.0 km/h. The average speed of student for whole journey is
4km/h
8/3 km/h
2.5 km/h
1.6 km/h
​

Answer 1

Answer:

1.6 km/h (Option D)

Explanation:

As per the provided information in the given question, we have :

• Distance from home to school = 4 km
• Speed of the student to go from home to school = 8 km/h
• Speed of the student to come from school to home = 4 km/h

We are asked to calculate the average speed.

In order to calculate the the average speed, firstly we need to calculate the total distance travelled and total time taken.

As the students goes from home to school and again comes back to home, so total distance will be the sum of the distance from home to school and from school to home.

$\longmapsto\rm {Distance_{(Total)} = (4 + 4) \; km }$

$\longmapsto \underline{\rm {Distance_{(Total)} = 8 \; km} }$

Now, we have to find the total time taken. The total time taken will be the sum of time time taken to cover the distance from home to school, the time he stayed there and time taken to come from school to home.

$\longmapsto\rm {Time_{(Total)} = T_{(H \; to \; S)} + 3.5 \; h + T_{(S \; to \; H)} }$

• H denotes home
• S denotes school

» Time = Distance ÷ Speed

$\longmapsto\rm {Time_{(Total)} = \Bigg ( \dfrac{4}{8}+ 3.5 +\dfrac{4}{4} \Bigg ) \; h}\\ \\ \longmapsto\rm {Time_{(Total)} = \Bigg ( \dfrac{1}{2}+ 3.5 +1 \Bigg ) \; h }\\ \\ \longmapsto\rm {Time_{(Total)} = \Bigg ( \dfrac{1+ 2 + 7}{2} \Bigg ) \; h }\\ \\ \longmapsto\rm {Time_{(Total)} =\dfrac{10}{2} \; h }\\ \\ \longmapsto \underline{\rm {Time_{(Total)} =5 \; h }}$

Now, as we know that,

$\bigstar \boxed{ \bf{Speed_{(Avg)} = \dfrac{Distance_{(Total)}}{Time_{(Total)}}} } \\ \\ \longmapsto \rm{Speed_{(Avg)} = \dfrac{8 \; km}{5 \; h} } \\ \\ \longmapsto \underline{\boxed{\rm{Speed_{(Avg)} = 1.6 \; km \; h^{-1}}}} \; \red {\bigstar}$

Therefore, the average speed of the student is 1.6 km/h.

Answer 2

Given :  A student goes from his home to school 4.0 km away with speed 8.0 km/h, stay in school for 3.5 h and returns back to home with speed 4.0 km/h.

To Find : The average speed of student for whole journey is

4 km/h

8/3 km/h

2.5 km/h

1.6 km/h

​

Solution:

Distance = Speed * Time

A student goes from his home to school 4.0 km away with speed 8.0 km/h

Time taken = 4/8 = 0.5 hrs

stay in school for 3.5 h  

Returns back to home with speed 4.0 km/h.  

Time taken =   4/4  =  1 Hrs

Total Distance = 4 + 4 = 8 hrs

Total Time =  2  + 3.5 + 0.5 = 5 hrs

The average speed of student for whole journey =  8/5 = 1.6 km/h

Learn  More:

The odometer reading of morning at 8:00 a.m. 36540 kilometre and ...

brainly.in/question/13815261

An express train takes 1 hour less than a passenger train to travel ...

brainly.in/question/15927656