Verified Answer :

\(\frac{2}{5}*40 =2*8=16 minutes\)
Have a nice day!!! ^^

Well, whenever OF is used in a mathematics, it mostly refers to multiplication. So basically, this means 2/5 x 40. So;
2/5 x 40
80/5. 
   when 5 divides 80, you get  16. So the answer to this is 16. Hope i helped. Have a nice day.