Question

Determine the greatest 5-digit number which is
exactly divisible by each of 8, 15 and 21.​

Answer 1

Step-by-step explanation:

the number which is divisible by these number will be thier LCM .

so the LCM of 8,15,21

by prime factorisation mehod,,,,

the prime factorisation of 8=2×2×2

15=3×5

21=3×7

so LCM =2³×3×5×7=840

now the greatest number of 5 digit is 99999.

now we have to find the number which is divisible by840 ...

so after dividing 99999 by 840

we get reminder 39

so if we substract 39 from the number it will be divisible...

so 99999-39=99960 will be the greatest 5 digit number which is divisible by8,15 and 21