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  • find the largest five digit number is exactly divisible by 7, 10, 15, 21 and 28 A)99840 B)99900 C)99960 D)99990

find the largest five digit number is exactly divisible by 7, 10, 15, 21 and 28 A)99840 B)99900 C)99960 D)99990

Answers (1)

LCM of 7,10,15,21, and 28 by prime factorization method
7 = 1x7
10 = 2x5 
15 = 3x5
21 = 3x7
28 = 2x2x7

LCM = 2x2x3x5x7 = 420
The number should be divisible by 420
Now, the largest five-digit number = 99999

99999 = 420 x 238 + 39

Hence the largest number divisible = 99999 - 39

                                                        = 99960.

Posted by

Ravindra Pindel

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