CBSE Class 10 Answered

Following are illustrative example, you can ask specific doubts.

Illustrative Examples

Example

Find the L.C.M. of 72, 240, 196.

Solution

Using Prime factorisation method
   72 = 2×2×2×3×3 = 2³×3²
   240 = 2×2×2×2×3×5 = 2⁴×3×5
   196 = 2×2×7×7 = 2²×7²
L.C.M. of the given numbers = product of all the prime factors of each of the given number with greatest index of common prime factors
     = 2⁴×3²×5×7² = 16×9×5×49 = 35280.

Example

Find the H.C.F. of 72, 126 and 270.

Solution

Using Prime factorisation method
    72 = 2×2×2×3×3 = 2³×3²
  126 = 2×3×3×7 = 2¹×3²×7¹
  270 = 2×3×3×3×5 = 2¹×3³×5¹
H.C.F. of the given numbers = the product of common factors with least index
  = 2¹×3² = 2×3×3 = 18

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