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Question
Find the least square number, exactly divisible by each one of the numbers:
(i) 6, 9, 15 and 20
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Solution
The smallest number divisible by 6, 9, 15 and 20 is their L.C.M., which is equal to 60.
Factorising 60 into its prime factors:
60 = 2 x 2 x 3 x 5
Grouping them into pairs of equal factors:
60 = (2 x 2) x 3 x 5
The factors 3 and 5 are not paired. To make 60 a perfect square, we have to multiply it by 3 x 5, i.e . by15.
The perfect square is 60 x 15, which is equal to 900.
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