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                 \ 09-Nov-2025  Bharat Arora   Proof-8                                     Reader’s Sign _______________________ Date __________

                example 2. Find the common factors of 12 and 20.

                Solution. 12 can be written as:                 20 can be written as:
                                 12 = 1 × 12                          20 = 1 × 20

                                 12 = 2 × 6                           20 = 2 × 10
                                 12 = 3 × 4                           20 = 4 × 5

                                     Factors                               Factors              6        1     5
                                                                                            3        2    4        10
                The factors of 12 are 1, 2, 3, 4, 6 and 12.
                                                                                                12            20
                The factors of 20 are 1, 2, 4, 5, 10 and 20.                            Factors                   Factors

                So, the common factors of 12 and 20 are 1, 2 and 4.                       of 12  Common factors   of 20

                            Exercise 5D

                    1.  Find the factors of the following numbers first and then write their common factors:

                        a.  6 and 10                                                              Common factors
                            Factors of 6 = ___________

                            Factors of 10 = ____________
                                                                                           Factors                Factors
                            Common factors = ___________                                    of 6                   of 10

                        b.  18 and 21                                                             Common factors

                            Factors of 18 = ___________
                            Factors of 21 = ___________                                    Factors                Factors

                            Common factors = ___________                                    of 18                  of 21

                        c.  10 and 20                                                             Common factors
                            Factors of 10 = ___________

                            Factors of 20 = ___________                                    Factors                Factors
                            Common factors = ___________                                    of 10                 of 20

                        d.  18 and 32                                                             Common factors

                            Factors of 18 = ___________
                            Factors of 32 = ___________                                    Factors                Factors

                            Common factors = ___________                                    of 18                  of 32

                    2.  Find the common factors of the following numbers.
                        a.  21 and 36            b.  18 and 54            c.  34 and 35            d.  15 and 25

                        e.  14 and 35            f.  56 and 64            g.  16 and 20            h.  18 and 40

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