CLEAR
Toprankers-Info

+91 7676564400

Mobile App

Get it on Google Play
Discussions
Tags:

Articles

Discussions
Submit Discussion
Raj

· started a discussion

· 1 Months ago

87373.0 (Question:87373.0)

Please explain the trick

Question:
 

 A car takes 1 hour less for a journey of 120 km, if its speed is increased by 10 kmph from its usual speed. What is its usual speed?

Options:
A) 30 kmph
B) 35 kmph
C) 20 kmph
D) 40 kmph
E) None of these
Solution:

Ans: (a) Let usual speed be s kmph and usual time be t hrs.
st = 120
s= 120/t      ..... (1)
New speed = s + 10 kmph
New time = t - 1 hrs.
then for a fixed distance s1 t1 = s2 t2

st = (s + 10)(t -1)
st = st - s + 10t - 10
s - 10t + 10 = 0
\(\cfrac{120}{t}\) - 10t - 10 = 0
120 - 10t2 +10t = 0
10t2 - 10t - 120 = 0
t2 - t - 12 = 0
(t - 4)(t + 3) = 0
t = 4 hrs.

From (1)
s = \(\cfrac{120}{4}\)  = 30 kmph.
 

-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