Subject: General Aptitude · Chapter: Time and Distance · Exam: · Marks: · Difficulty:
What is the average speed of the car over the entire distance? I. The car covers the whole distance in four equal stretches at speeds of 10 kmph, 20 kmph, 30 kmph and 60 kmph respectively. II. The total time taken is 36 minutes.
Answer
SELF-PRACTICE — the source book printed no answer.
Nothing is invented here, so this question has no answer on record.
Explanation
Let the whole distance be $4x$ km. I. Total time taken $=\left(\frac{x}{10}+\frac{x}{20}+\frac{x}{30}+\frac{x}{60}\right)=\frac{(6x+3x+2x+x)}{60}=\frac{12x}{60}=\frac{x}{5}$. $\therefore$ Speed $=\frac{\text{Distance}}{\text{Time}}=\frac{4x}{(x/5)}$ kmph $=20$ km/hr. $\therefore$ I alone is sufficient to answer the question. II. alone does not give the answer. $\therefore$ Correct answer is (a).
Explanation as extracted from the printed page; notation may be imperfect.