Number Analogies :
Typical relationships between the numbers in a given
pair can be any of the following :
·
One
number is a multiple of the other.
·
One
number is the square or square root of the other.
·
One
number is the cube or cube root of the other.
·
The
two numbers are squares of two other numbers which themselves are related. For
example, the two numbers are squares of two consecutive integers or squares of
two consecutive even integers or squares of two consecutive odd integers.
·
The
two numbers are such that they are obtained by subtracting a certain number
from the squares or cubes of the two related numbers.
·
The
two numbers are such that they are obtained by adding a certain number to the
squares or cubes of the two related numbers.
·
The
two numbers can be consecutive, even, odd or prime numbers.
There
can be many more combinations that one can think of but the student has to note
an important point in solving questions on Number Analogies. In Number Series
related questions, since a series of numbers (more than two numbers) will be
given, the relationship or pattern can be identified uniquely. In Number
Analogies, since only two numbers are given, it may be possible to think of
more than one relationship existing between the two numbers in the given pair.
But, it should be kept in mind that generally, simple addition of one number or
subtraction of one number is not what is given in Number Analogies. The
questions try to test the insight that the student has got into the
relationship between the numbers.
Let us take a few examples and understand the questions
on Number Analogies.
Worked out examples :
Example 1.
Find the missing number.
25 : 36 : : 49 : ______.
(a) 61
(b) 63
(c) 65
(d) 60
Solution.
When
the numbers in the question are considered the students tend to consider 25 and
36 as squares of two consecutive natural numbers. But the answer choices does
not consist of an answer suitable to the above logic. Hence, it is important
that, the student keeps the answer Choices in view in arriving at the logic.
25
+ 11=36
Similarly,
49 + 11 = 60
Choice
(d)
Example 2.
Find the missing number.
27 : 51 : : 83 : ________.
(a) 102
(b)117
(c) 123
(d) 138
Solution.
The given analogy can be written as
52 + 2 : 72 + 2 : : 92
+ 2 : _____.
5 and 7 are successive odd numbers.
Similarly, next odd number to 9 is 11 and
112+ 2= 121+2= 123. .
Choice (c)
Example 3.
Find the missing number.
11 : 25 : : 17 : _____.
(a) 33
(b) 28
(c) 41
(d) 37
Solution.
11 × 2 + 3 = 22 + 3 = 25
Similarly,
17 × 2 + 3 = 34+ 3 = 37.
Choice
(d)
