kpk 40 72 120 dan 21 28 35 tolong dbtu kk

            40              72                120
             ^                ^                    ^
          2   20          2  36              2  60
                 ^               ^                     ^
               2  10        2   18              2   30
                    ^                ^                     ^
                 2    5           2  9                2   15

        = 2³ x 5            = 2³ x 9          = 2³ x 15

KPK =  2³ x 5 x 9 x 15
        = 5.400

                21                  28                35
                 ^                    ^                   ^
               3   7              2   14            5   7
                                         ^
             = 3 x 7               2  7           = 5 x 7
                              = 2² x 7

KPK = 2² x 3 x 5 x 7
        = 420