# Online Coaching For RRB Exam Reasoning (Mathematical Operations)

## Reasoning (Mathematical Operations)

The basic approach for the problems of this type is more or less similar to that of coding and decoding. One has to study the symbols or the geometrical figures and their meanings carefully. Then, the meanings are to be used in place of those symbols in answering the questions.

The questions can be categorised into two types:

## Symbols and Notations Example 2: If 2 * 3 = 12, 3 * 4 = 20 and 4 * 5 = 30, then 2 * 6 is

(a) 18
(b) 12
(c) 21
(d) None of these

Solution. (c) The numbers on both sides of * are increased by one and then multiplied to get the answer.

2*6 = 3 × 7 = 21

Example 3: If x + y = (x + y + xy –1) (x + y + xy + 1), then the value of (4 \$ 10) is

(a) 2915
(b) 2195
(c) 2951
(d) 2955

Solution. (a) As per the definition of +, (4+10) would be (4 + 10 + 4 × 10 – 1) (4 + 10 + 4 × 10 + 1) = 2915. So, answer is (a)

Example 4: If * means “is greater than”, @ means `is less than’; and \$ means “is equal to” and if a + b and b @ c, then

(a) c * b
(b) b * c
(c) c * a
(d) Both (a) and (c)

Solution. (d) Replace the symbols with the meaning given against them. If a \$ b and b @ c would become a = b and b < c, then c > b or c > a ie, c * b, c * a are true from the given options.

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