CLEAR
Toprankers-Info

+91 7676564400

Mobile App

Get it on Google Play
Discussions
Select Date
Tags:

Articles

Discussions
Submit Discussion
Nishant Singh

· started a discussion

· 1 Months ago

When to use 2xy/x+y to calculate average speed? (Question: 97568.0 )

Sir you have calculated average speed of x and 3x as 2x taking mean of it.But I have read that average speed formula is 2xy/x+y and according to it average speed is 3/2x.Why such difference?

Question:
The speed of a car during the second hour of its journey is thrice that in the first hour. Also its third hours speed is the average speed of the first two hours. Had the car travelled at the second hour’s speed during all the first three hours, then it would have travelled 150 km more. Find the percentage reduction in time if the original distance covered by second hour’s speed:
Options:
A) \(33\frac{1}{3}\%\)
B) 40%
C) 25%
D) 50%
Solution:

Ans: (a)               

                       First               Second       Third      Total

                       hour                 hour         hour

Initial speed       x                     3x          2x             6x

New speed         3x                   3x          3x             9x

∴ Percentage increase in speed = \(\cfrac{3x}{6x}\) × 100 = 50%

Since speed is increased by (50%)  \(\cfrac{1}{2}\)

Therefore, time will reduce by (33.33%) \(\cfrac{1}{3}\)

Knowledge Expert

· commented

· 1 Months ago

Dear Student, its because Speed is inversely proprtional to Time Keep Learning with Us Best Wishes Team Toprankers
-logo
We at aim to provide most comprehensive content & test for practice which is carefully divided into various chapters and topics to help you focus on your weak areas.Our Practice mock test gives you unmatched analytics to help you realize your strong areas,time management and improvement areas.Our Short & Crisp notes on each topic will help you to quickly revise the topic along with the tips & tricks of the exams.
More About
-Info
-Info

Mobile App

Get it on Google Play
About Us Campus Ambassador Careers Contact Us Refund Policy

All Rights Reserved Top Rankers

User Policy
Disclaimer
Terms & Conditions