The submarine, moving at a speed of 15.6 km / h, arrived at its destination in 3 hours 45 minutes.

The submarine, moving at a speed of 15.6 km / h, arrived at its destination in 3 hours 45 minutes. How fast did she have to go to go all the way 30 minutes faster?

The solution of the problem:
1. It is necessary to convert the time into hours.
3 hours 45 minutes = 3 + 45/60 = 3.75 hours
The boat should go all the way thirty minutes faster.
30 minutes is 3 hours 45 minutes-30 minutes = 3 hours 15 minutes = 3 + 15/60 = 3 hours 25 minutes
We know that the higher the speed, the less time it takes to travel, which means that speed and time are inversely proportional.
let’s make a proportion:
3.75 / X = 3.25 / 15.6
X = (3.75 * 15.6) / 3.25
X = 18 km / h
Answer: A boat must go at a speed of eighteen kilometers per hour to go all the way thirty minutes faster.