The task is to generate the correct answer for a given math problem.

Ex Input:
Problem: two pipes can fill the cistern in 10 hr and 12 hr respectively , while the third empty it in 30 hr . if all pipes are opened simultaneously , then the cistern will be filled in

Ex Output:
6.67 hr


Ex Input:
Problem: the ratio of the radius of two circles is 1 : 3 , and then the ratio of their areas is ?

Ex Output:
1 : 9


Ex Input:
Problem: the perimeter of an isosceles right triangle is 12 + 12 sq rt 2 . what is the length of the hypotenuse of the triangle ?

Ex Output:

8.485', 'e ) 8'