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SAI International School

                                                       CLASS – VI

           Mathematics

           Chapter-12: Ratio and Proportion-2
           Lesson Notes - 2
           SUBTOPICS:


               1) Proportion
                        If two ratios are equal, we say that they are in proportion and use
                         the symbol ‘::’ or ‘=’ to equate the two ratios.
                        If two ratios are not equal, then we say that they are not in proportion.
               2) Parts of a Proportion
                        In a statement of proportion, the four quantities involved when taken in order are
                         known as respective terms.
                        First and fourth terms are known as extreme terms.
                        Second and third terms are known as middle terms.

















               3) Methods to check whether the given ratio are in proportion or not
                  Method -1: By converting the ratio to lowest form
                  4. Determine if the following ratios form a proportion. (NCERT, Ex-12.2, Pg-256)
                  (a) 25 cm : 1 m and Rs 40 : Rs 160

                         25 cm : 1 m = 25 cm: 100 cm =       =   = 1: 4


                          Rs 40 : Rs 160 =    =   = 1 : 4

                        As 25 cm : 1 m = Rs 40 : Rs 160 = 1:4
                  So, 25 cm : 1 m :: Rs 40 : Rs 160

                  Method -2: By using the formula
                  Two ratios say a:b and c: d are said to be in proportion if the
                         product of their means = the product of their extremes
                                        i.e b x c = a x d
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