# physics

a boy walks to a school at a rate of 6km with a speed of 2.5km/h and walks back with a constant speed of 5km/h. his average speed for round trip in km/h is ?

1. 👍 0
2. 👎 0
3. 👁 243
1. You must mean that the rate of walking to school is 6 km/h, not 6 km.

Let the distance to school be D. (It will cancel out when you compute the avg. speed)

avg speed = (total distance covered)/(total time)
= 2D/[D/6 + D/2.5}
= 2/[(1/6 + 4/10]
= 2/[5/30 + 12/30]
= 60/17 = 3.53 km/h

Note that this is NOT the average of 6 and 2.5. He spends more time walking at the lower speed.

1. 👍 0
2. 👎 0

## Similar Questions

1. ### Precalculus

Hello, An Aircraft carrier can travel 450km in the same time a container ship travels 300km. If the aircraft carrier was traveling 5km/h faster what was the speed of the container ship? I don't need help answering the actual

asked by Kayla on January 4, 2019
2. ### physics

a boy walks to his school at a distance of 6km with constant speed of 2.5 k mph and walks back with a constant sped of 4 k mph. His average speed of round trip expressed in k mph is?

asked by srikala on May 25, 2012
3. ### Word Equations

Yochanan walked from home to the bus stop at an average speed of 5km/h. He immediately got on his school bus and traveled at an average speed of 60km/h until he got to school. The distance from his home to school is 35 kilometers,

asked by Ta'Shanna on March 18, 2016
4. ### Calculus

A man 2m tall walks away from a lamppost whose light is 5m above the ground. If he walks at a speed of 1.5m/s, at what rate is his shadow growing when he is 10m from the lamppost? I tried to draw a diagram, but I don't understand

asked by sh on December 1, 2009
5. ### Calculus-rates

1.) A man 6 ft tall walks at a rate of 5 ft per sec. from a light that is 15 ft above the ground. At what rate is the top of his shadow changing? 2.) An airplane flies at an altitude of 5 miles toward a point directly over an

asked by Amy on May 5, 2011
1. ### math

A student starts from A and walks 3km east to B, she then walk 5km on a bearing 152 degree from 13 . She reaches a point c . Find the distance and bearing of C from A.

asked by joy on May 25, 2017
2. ### Physics

A boy moves 10km eastwards, 5km northwards and then 2km eastwards. The distance and magnitude of displacement of the boy is

asked by Anhigna on July 10, 2015
3. ### maths

sita and gita start walking from the same point on the road but in opposite directions.if sita walks at the speed of 5km/h and gita @ a speed of 4km/h,in how much time will they be 27km apart

asked by Anonymous on December 20, 2012
4. ### physics

a boy of mass 'm' stands on one end of a wooden plank of length L and mass M. The plank is floating on water. If the boy walks from one end of the plank to the other end at a constant speed the resulting displacement of the plank

asked by shoaib on June 25, 2010
5. ### physics

A man walks 5km south and then 3km in the direction 60degrees west of south.His distance from the starting point is?

asked by anonymous on September 17, 2019
6. ### Math

An orienteer runs for 4.5km, then turns through and angle of 32 degrees and runs for another 6km.How far is she from her starting point?

asked by Jeremy on April 22, 2015