Cheenta
How 9 Cheenta students ranked in top 100 in ISI and CMI Entrances?
Learn More

Calculating Average Speed | Tomato Problem 3

This is a problem number 3 from TOMATO based on Calculating Average Speed.

Problem: Calculating Average Speed.

A boy walks from his home to school at 6 kmph. He walks back at 2 kmph. His average speed, in kmph is
(A) 3; (B) 4; (C) 5; (D) $\sqrt {12}$;

Discussion: 

Suppose the distance from home to school is t km.
Time taken for home to school journey: $\frac {t}{6}$
Time taken for school to home journey: $\frac {t}{2}$

Hence average speed = $\frac {distance}{time} = \frac {2t}{\frac{t}{6} + \frac{t}{2}} = 3$

There fore average speed is 3 kmph.

Note that it is the harmonic mean of the two given speeds instead of arithmetic mean.

Chatuspathi:

  • What is this topic: Elementary Arithmetic
  • What are some of the associated concepst: Harmonic Mean
  • Where can learn these topics: Cheenta I.S.I. & C.M.I. course, discusses these topics in the ‘Number Theory’ module.
  • Book Suggestion: Arithmetic by K.C. Nag

Knowledge Partner

Cheenta is a knowledge partner of Aditya Birla Education Academy
Cheenta

Cheenta Academy

Aditya Birla Education Academy

Aditya Birla Education Academy

Cheenta. Passion for Mathematics

Advanced Mathematical Science. Taught by olympians, researchers and true masters of the subject.
JOIN TRIAL
support@cheenta.com