Topic outline

    • Playing With Numbers

      Exercise 2.9 (Lowest Common Multiple – L.C.M)

      Question 1 (Refer Book - Mathematics Class VI R.D. Sharma)

      Solution:

      i. 48, 60

      We have,

       

      2

      48, 60

      2

      24, 30

      3

      12, 15

      2

       4,   5

      2

       2,   5

      5

       1,   5

       

       1,   5

       

      Therefore, L.C.M of given numbers = 2x2x2x2x3x5 = 240

       

       



      ii. 42, 63

      We have,

       

      21

      42, 63

      2

       2,   3

      3

       1,   3

       

       1,   1

       

      Therefore, L.C.M of given numbers = 21x2x3 = 126

       

       

      iii. 18, 17

      We have,

       

      17

      18, 17

      2

      18,  1

      3

       9,   1

      3

       3,   1

       

       1,   1

       

      Therefore, L.C.M of given numbers = 17x2x3x3 = 306

       



      iv. 15, 30, 90

      We have,

       

      3

      15, 30, 90

      5

       5,  15, 30

      3

       1,   3,  6

      2

       1,   1,  2

       

       1,   1,   1

       

      Therefore, L.C.M of given numbers = 3x5x3x2 = 90

       

       

      v. 56, 65, 85

      We have,

       

      5

      56, 65, 85

      2

      56, 13, 17

      2

      28, 13, 17

      2

      14, 13, 17

      7

       7,  13, 17

      13

       1,  13, 17

      17

       1,   1,  17

       

       1,   1,  1

       

      Therefore, L.C.M of given numbers = 2x2x2x5x7x13x17 = 61880

       

       



      vi. 180, 384, 144

      We have,

       

      2

      180, 384, 144

      2

       90,  192,  72

      2

       45,   96,   36

      2

       45,   48,   18

      3

       45,   24,    9

      3

       15,    8,    3

      2

        5,     8,    1

      2

        5,     4,    1

      2

        5,     2,    1

      5

        5,     1,    1

       

        1,     1,    1

       

      Therefore, L.C.M of given numbers = 2x2x2x2x2x2x2x3x3x5 = 5760

       

       

      vii. 108, 135, 162

      We have,

       

      3

      108, 135, 162

      3

       36,   45,  54

      3

       12,   15,  18

      2

        4,     5,    6

      2

        2,     5,    3

      3

        1,     5,    3

      5

        1,     5,    1

       

        1,     1,    1

       

      Therefore, L.C.M of given numbers = 2x2x3x3x3x3x5 = 1620

       

       



      viii. 28, 36, 45, 60

      We have,

       

      2

      28, 36, 45, 60

      2

      14, 18, 45, 30

      3

       7,   9,  45, 15

      3

       7,   3,  15,  5

      5

       7,   1,   5,   5

      7

       7,   1,   1,   1

       

       1,   1,   1,   1

       

      Therefore, L.C.M of given numbers = 2x2x3x3x5x7= 1260