SSC CGL (Prelims) Maths: Speed, Time and Distance questions with solutions

Q1. If a man can cover 40 km in 5 hours, what is his average speed?

1. 8 km/h
2. 10 km/h
3. 6 km/h
4. 7.5 km/h

Answer: 8 km/h

Average speed is calculated as distance divided by time. Here, $40 \div 5 = 8$, so the speed is 8 km/h.

Q2. A person travels by car from city A to city B at an average speed of 63 km/h and returns at an average speed of 42 km/h. His average speed for the whole journey is:

1. 52.5 km/h
2. 55.4 km/h
3. 48.5 km/h
4. 50.4 km/h

Answer: 50.4 km/h

Since the person travels the same distance each way, the average speed is not the arithmetic mean. Use the formula \(\frac{2ab}{a+b}\) with speeds 63 and 42. This gives \(\frac{2 \times 63 \times 42}{63+42} = 50.4\) km/h.