Therefore, the greatest common divisor of 12 and 16 = 4
Note : 1. The product of the G.C.D and L.C.M of two numbers is equal to the
product of the two numbers.
- The G.C.D of two prime numbers is 1.
- The L.C.M of two prime numbers is their product.
The idea of finding the G.C.D of numbers can be explained to the child orally. In
addition, the pre-requisite for effective understanding of the idea is the mastery of
the mathematical tables. If the child is not comfortable with mathematical tables,
the concept can be taught through the beads also.
Say for instance, to find the G.C.D of 15 and 18 ask the child to list all the divisors of
15 and the divisors of 18 separately.
The divisors of 15 are 1, 3, 5, 15
The divisors of 18 are 1, 2, 3, 6, 9, 18
As the divisors of 15 and 18 are grouped in the form of beads separately, on exploration
the child will be able to list the common divisors, that is, 1 and 3. Now, among the
common divisors, the greatest, which is 3, is the G.C.D.
- Number line
Number line is a graphical representation of the integers, wherein zero takes the
middle place, positive numbers to the right of zero and negative numbers to the left
of zero. In the right, the value of a number increases when moving away from zero,
and in the left the value of a number decreases while moving away from zero.
Numbers with ‘+’ sign are called positive numbers and numbers with ‘-’ sign are
called negative numbers.
Note that since zero corresponds to the origin it does not involve any direction and
hence zero is neither negative nor positive.
- 5 - 4 - 3 - 2 - 1 0 1 2345
