Quantitative Aptitude Ques 791
Question: Speed of motorboat in still water is 45 km/h. If the motorboat travels 80 km along the stream in 1 h 20 min, then the time taken by it to cover the same distance against the stream will be
Options:
A) 3 h
B) 1 h 20 min
C) 2 h 40 min
D) 2 h 55 min
Show Answer
Answer:
Correct Answer: C
Solution:
- Let the speed of the current $ =xkm/h $
$ \therefore $ Rate downstream $ =(x+45)km/h $ According to the question, $ \frac{80}{x+45}=1h20\min =\frac{4}{3}h $
$ \Rightarrow $ $ 4x+180=240 $
$ \Rightarrow $ $ 4x=240-180=60 $
$ \Rightarrow $ $ x=\frac{60}{4}=15km/h $ Rate upstream $ =45-15=30km/h $
$ \therefore $ Required time $ =\frac{80}{30}h=2h40\min $
BETA
