27 Views

Question : Nikunj goes 4 kilometres against the current of a stream in 1 hour, and 2 kilometres along the current in 15 minutes. How long will it take him to go 7 kilometres in stationary water?

Option 1: 1 hour 15 minutes

Option 2: 1 hour 20 minutes

Option 3: 1 hour 10 minutes

Option 4: 1 hour 5 minutes


Team Careers360 8th Jan, 2024
Answer (1)
Team Careers360 15th Jan, 2024

Correct Answer: 1 hour 10 minutes


Solution : Let the speed of Nikunj in still water as V (in km/h), and the speed of the stream as S (in km/h).
When Nikunj goes against the current, his effective speed
⇒ V − S = $\frac{4}{1}$ = 4 km/h
When he goes along the current, his effective speed is
⇒ V + S = $\frac{{2}}{\frac{1}4}$ = 8 km/h
Now,
⇒ V − S +  V + S = 4 + 8
⇒ 2V = 12
⇒ V = $\frac{12}{2}$ = 6 km/h
Also
Time taken for a distance of 7 km,
⇒ Time = $\frac{\text {Distance}}{\text{Speed}}$ = $\frac{7}{6}$ hours = 1 hour 10 min
Hence, the correct answer is 1 hour 10 min.

Know More About

Related Questions

TOEFL ® Registrations 2024
Apply
Accepted by more than 11,000 universities in over 150 countries worldwide
Manipal Online M.Com Admissions
Apply
Apply for Online M.Com from Manipal University
View All Application Forms

Download the Careers360 App on your Android phone

Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile

150M+ Students
30,000+ Colleges
500+ Exams
1500+ E-books