The motor ship sailed 180 km in 6 hours. How much do you need to increase the speed

The motor ship sailed 180 km in 6 hours. How much do you need to increase the speed of the ship so that it travels the same distance in 4 hours.

Let’s determine with what speed the ship was sailing initially.
V1 = S * t1 = 180/6 = 30 km / h.
Let’s denote the new speed through V2, then:
S = V2 * t2 = V2 * 4.
Since the path has not changed, then S = 180 km.
180 = V2 * 4.
V2 = 180/4 = 45 km / h.
Let’s find the speed difference.
V2 – V1 = 45 – 30 = 15 km / h.
Answer: The speed should increase by 15 km / h.