Question

A bus takes 3 hours and 30 minutes to cover a distance of 280 km. To make this journey in 4 hours, by how much the speed of the bus be decreased?

• A. 12 kmph
• B. 8 kmph
• C. 10 kmph
• D. 15 kmph

Hint:

To calculate speed decrease, first find the original speed and the desired speed, then subtract the two values.

Answer 1

The Correct Option is C

The first step is to calculate the original speed of the bus. The bus takes 3 hours and 30 minutes to cover 280 km. To convert 30 minutes into hours, we get: \[ 3 \, \text{hours} + \frac{30}{60} \, \text{hours} = 3.5 \, \text{hours} \] Now, the original speed of the bus is: \[ \text{Speed} = \frac{\text{Distance}}{\text{Time}} = \frac{280 \, \text{km}}{3.5 \, \text{hours}} = 80 \, \text{km/h} \] Next, the desired time for the journey is 4 hours. To find the new speed required to complete the journey in 4 hours, we use the formula: \[ \text{New Speed} = \frac{280 \, \text{km}}{4 \, \text{hours}} = 70 \, \text{km/h} \] Now, the decrease in speed is: \[ \text{Decrease in Speed} = 80 \, \text{km/h} - 70 \, \text{km/h} = 10 \, \text{km/h} \] Thus, the speed of the bus needs to be decreased by 10 km/h. Therefore, the correct answer is (3) 10 km/h.