A girl walks 12 km at the speed of 3 km/h. what change should she make in her speed to take (i) an hour less and (ii) an hour more to cover the distance?
d = r*t = 12 km
3 * t = 12
t = 4 h
1. d = r*t = 12
r * 3 = 12
r = 4 km/h
Change = 4 - 3 = 1 km/h = 1 km/h increase.
2. d = r*t = 12 km
r * 5 = 12
r = 2.4 km/h.
Change = 2.4 - 3 = -0.6 km/h = 0.6 km/h
decrease.
It really helped me!!
To find the change in speed required to take (i) an hour less and (ii) an hour more to cover the distance, we need to understand the relationship between speed, time, and distance.
The formula to calculate distance is:
Distance = Speed × Time
Let's break down the problem into two parts:
(i) To take an hour less to cover the distance:
- The speed remains unknown, so we'll call it 'x' km/h.
- The time taken will be (3 hours - 1 hour) = 2 hours.
- The distance covered is given as 12 km.
Using the formula Distance = Speed × Time, we can write the equation as:
12 km = x km/h × 2 hours
To solve for 'x', we divide both sides of the equation by 2 hours:
12 km / 2 hours = x km/h
6 km/h = x
Therefore, to take an hour less to cover the distance, she should increase her speed to 6 km/h.
(ii) To take an hour more to cover the distance:
- The speed remains unknown, so we'll call it 'y' km/h.
- The time taken will be (3 hours + 1 hour) = 4 hours.
- The distance covered is given as 12 km.
Using the formula Distance = Speed × Time, we can write the equation as:
12 km = y km/h × 4 hours
To solve for 'y', we divide both sides of the equation by 4 hours:
12 km / 4 hours = y km/h
3 km/h = y
Therefore, to take an hour more to cover the distance, she should decrease her speed to 3 km/h.