Subject: General Aptitude · Chapter: Time and Distance · Exam: · Marks: · Difficulty:
To reach point B from point A. At 4pm, Sara will have to travel at an average speed of 18 kmph. She will reach point B at 3 pm if she travels at an average speed of 24 kmph. At what average speed should Sara travel to reach point B at 2pm? [IBPS-Bank PO/MT (Pre.) Exam, 2015]
(a)36 kmph
(b)28 kmph
(c)25 kmph
(d)30 kmph
Answer
Answer (as printed): A
Explanation
Difference between time = 1 hour. Distance between point $A$ and $B$ = $x$ km. According to the question, $$\frac{x}{18}-\frac{x}{24}=1$$ LCM of 18 and 24 = 72. $$\Rightarrow \frac{4x-3x}{72}=1 \Rightarrow x=72\text{ km}.$$ Time taken at 18 km/ph to cover 72 km $=\frac{72}{18}=4$ hours. $$\therefore \text{Speed to cover 72 km in 2 hours} = \frac{72}{2} = 36\text{ km/ph}.$$
Explanation as extracted from the printed page; notation may be imperfect.