Q:  The lifetime of the Sun is about 10 billion years.

      What is the lifetime of a star of 10 solar masses?

                                        1    2
          L  =  10 billion years *  ( ----- )     =  100 million years
                                        10


      
      What is the lifetime of a star of 20 solar masses?

                                        1    2
          L  =  10 billion years *  ( ----- )     =   25 million years
                                        20