Question

A boat travels for 7 hours. if it travels 4 hours downstream and 3 hours upstream. ten t covers a distance of 116 km. but if it travels 3 hours downstream and 4 hours uptream, it covers the distance of 108 km. find the speed of the boat.

Answer 1

Speed = Distance / Time
Distance = Speed*Time

For this problem, we should bear in mind that current speed has an impact on the boat speed...

for upstream, the boat goes against the current, and so its speed is

U = V - C

where V is the speed of the boat
C is the current speed

for downstream, it will be:

D = V + C

Convert the problem into mathematical equations:

4D + 3U = 116
3D + 4U = 108

4(V+C) + 3(V-C) = 116
4V + 4C + 3V -3C =116
7V + C = 116

3(V+C) + 4(V-C) = 108
3V + 3C + 4V - 4C = 108
7V - C = 108

Solving the equations:

7V + C = 116
7V - C = 108

14V = 224
V = 16km/hr —-> speed of boat

to get C:
7(16) + C = 116
C = 4km/hr