Question

Kiran starts at 9:00 am by bicycle to reach office. She cycles at the speed of 8 km/hour and reaches the office at 9:15 am. By how much should she increase the speed so that she can reach the office at 9:10 am?

Answer 1

she should increase the speed by 4 km/hour (that is increase the speed to 12 km/hour) to reach the office at 9:10 am.

Explanation:

From the question,

• Kiran starts at 9:00 am and reaches the office at 9:15 am

Hence, she spent 15 minutes to the office

Time, t = 15 mins (Convert this hour)

15 mins = (15/60) hour = 0.25 hour

• Also, she cycles at the speed of 8 km/hour

That is, speed, v = 8 km/hour

First, we will find the distance she traveled,

From,

`Speed = (Distance)/(Time)`

Then,
`Distance = Speed * Time`

Hence,

`Distance = 8km/hour * 0.25 hour`

`Distance = 2 km`

Hence, the distance she traveled is 2km.

Now, to determine how much she should increase the speed to reach the office at 9:10 am

That is, we will find the speed to reach the office in 10 minutes

Hence, Time = 10 mins (convert to hour)

10 mins = (10/60) hour = 1/6 hour

The distance she is to travel is the same.

That is, distance = 2 km

Now, to determine the speed.

From,

`Speed = (Distance)/(Time)`

`Speed = (2 km)/((1)/(6)hour )`

`Speed = 12 km/hour`

To reach the office at 9:10 am, she must travel at a speed of 12 km/hour.

Hence, she must increase the speed by (12 - 8) km/hour = 4 km/hour.

Answer 2

4km/h

Explanation:

Given data

speed = 8km/h

time taken= 9 am- 9:15 am = 15 mins

convert 15 mins to hours= 1/60*15 = 0.25 hrs

we can now calculate the distance

speed= distance/time

8= d/0.25

d= 8*0.25

d= 2km

now for Kiran to arrive in 10min (0.16 hrs), since the distance is 2 km

let us find the speed

speed= d/t

speed= 2/0.166

speed= 12.0km/h

Hence she needs to increase her speed by 12-8= 4km/h