Number System
Test of divisibility:
1. A number is divisible by ‘2’ if it ends in
zero or in a digit which is a multiple of
‘2’
i.e. 2, 4, 6, 8.
2. A number is divisible by ‘3’, if the sum of
the digits is divisible by ‘3’.
3. A number is divisible by ‘4’ if the number
formed by the last two digits, i.e. tens
and
units are divisible by 4.
4. A number is divisible by ‘5’ if it ends in
zero or 5
5. A number is divisible by ‘6’ if it divisible
by ‘2’ as well as by ‘3’.
6. A number is divisible by ‘8’ if the number
formed by the last three digits, i.e,
hundreds tens and units is divisible by ‘8’.
7. A number is divisible by ‘9’ if the sum of its
digit is divisible by ‘9’
8. A number is divisible by ‘10’ if it ends in
zero.
9. A number is divisible by ‘11’ if the
difference between the sums of the digits in
the
even and odd places is zero or a multiple of ‘11’.
LCM:LCM of a given set of numbers is the least number which is exactly
divisible
by every number of the given set.
HCF:HCF of a given set of numbers is the highest
number which divides exactly
every n umber of the given set
.