Question 28453
Since you know that an hour has 60 minutes, you can say that the plane travels 560k in 60 min. (or 560 / 60).  You also know that the plane has only traveled 140k and you need to know the min.  Use "x" for unknown min. You get the following equation.

(560/60) = (140/x)

Now you can use cross multiplication to solve for "x"
(It helps to write the problem in columns <i.e. 560 over the 60>)

If you cross multiply, you get

560x = 60(140)
560x = 8400

Divide both sides by 560

x = 15
 
Hope it helps.  :)