A car drives 90 km at 45 km/h and returns the same 90 km at 30 km/h. What is its average speed over the whole trip?
Answer and explanation
Correct answer: C. 36 km/h
- Step 1: Total time = 90/45 + 90/30 = 5 h. Step 2. Average speed = 180 / 5 = 36 km/h. Answer: 36 km/h. Why not the others: 37.5 km/h: the simple average of the speeds was used. 75 km/h: the speeds were added. 18 km/h: only one leg of the distance was used.
Practise more Quantitative Reasoning.
Free questions with an explanation for every one, and full timed Sciences Po and Grandes Ecoles Entrance Practice mock tests.
More Quantitative Reasoning questions
- 75 euros are shared between two people in the ratio 4 : 1. How much does the first person receive?
- 200 euros are shared between two people in the ratio 3 : 2. How much does the first person receive?
- A price of 1200 euros rises by 5 % and then falls by 5 %. What is the final price?
- 100 euros are shared between two people in the ratio 1 : 4. How much does the first person receive?
- 6 workers need 10 days for a job. How many days would 5 workers need at the same pace?
- The share of a party in the polls goes from 60 % to 54 %. By how many percentage points does it change (absolute value)?