How do I solve this?

Question

A ship must average 22 knots (nautical miles per hour) to make its 10-hour run on schedule. During the first 4 hours bad weather has caused it to reduce its speed to 16 knots. What should it's average speed be for the rest of its trip to maintain its schedule?

Answer 1

The distance travelled at 22 knots for 10 hours is 220 nautical miles total distance

 

We have travelled 16 knots for 4 hours = 64 nautical knots

 

220 - 64 = 156 nautical miles to go in 6 hours

 

rate = distance/time .... distance = 156, time = 6 hours

 

r = 156/6 = 26 knots