A Nile cruise ship takes 21.7 h to go upstream from Luxor to Aswan, a distance of 208 km, and 20.3 h to make the return trip downstream. Assuming the ship's speed relative to the water is the same in both cases, calculate the speed of the current in the Nile.

Answer 1

(Vs-Vc)t1 = 208 km.
(Vs+Vc)t2 = 208 km.

Vs*t1-Vc*t1 = 208
Vs*t2+Vc*t2 = 208

Eq1: 21.7Vs - 21.7Vc = 208
Eq2: 20.3Vs + 20.3Vc = 208
Multiply Eq1 by 20.3 and Eq2 by 21.7 and
add the Eqs:
440.51Vs - 440.51Vc = 4222.4
440.51Vs + 440.51Vc = 4513.6
Sum: 881.02Vs = 8736
Vs = 9.92 km/h = Velocity of the ship.

In Eq1, replace Vs with 9.92 and solve for Vc(Velocity of the current.).