please solve this question

Question

In the past 5 hours a boat has traveled at an average speed of 10.2 miles per hour. How fast would it have to travel in the next hour to average 12 miles per hour?

Answer 1

Speed = distance / time

 

10.2 = distance / 5

 

distance = 51 miles

 

let  in next hour boat travel x miles

 

so distance = 51 + x

 

average speed should be 12 mi/ hr

 

now time = 5+1 =6

 

 

12 = 51+x / 6

 

 72 = 51+x

 

x = 21

 

so boat traveled 21 miles in next hour

 

so speed = 21 / 1 = 21 mi/hr