Mathematical Operations - Interchanging of Symbols


 
 
Concept Explanation
 

Mathematical Operations - Interchanging of Symbols

Mathematical Operations:  As you know that in the questions based on simple mathematical operations the four fundamental mathematical operations that is addition, subtraction, multiplication and division and relational operators that is less that, more than etc are to be rearranged to get the desired result.

Making Equation Correct by Interchanging the Symbols: In these type of questions certain equations are written and the candidate is asked to interchange the position of the symbols or numbers so that the equation becomes correct.

Illustration: In the following question , the given equation becomes correct after interchanging two signs. One of the four alternatives under it specifies the interchange of signs in the equation which when made will make the equation correct. Find the correct alternative.

9+5div 4times 3-6=12

A. + and x                 B. div and x                 C. div and -                    D. + and -

Answer: C

Solution: On interchanging div and -, we get

L.H.S.=9+5-4times3div6

=9+5-4times frac{1}{2}

= 9 + 5 -2

= 12 = R.H.S.

Illustration: In the following question , the given equation becomes correct after interchanging two signs. One of the four alternatives under it specifies the interchange of signs in the equation which when made will make the equation correct. Find the correct alternative.

 (6-3) + (4 times 2 + 13)div (7 times 2)=21

A.  + and -                   B. times ;; and ;; div                    C.  div ;; and ;; +              D.  times ;; and ;; -

Answer : D

Solution: On interchanging times ;; and ;; -, we get

(6-3) + (4 times 2 + 13)div (7 times 2)=21

L.H.S. = (6times3) + (4-2 + 13)div (7 - 2)

= 18 + 15div 5

= 18 + 3 = 21= R.H.S.

Illustration: If the given interchanges namely : signs + and div and numbers 2 and 4 are made in signs and numbers, which one of the following four equations would be correct ?

(a)  2 + 4 div 3 = 3                  (b)  4 + 2 div 6 = 15               (c)  4 div 2 + 3 = 4             (d) 2 + 4 div 6 = 8

Answer: D

Solution : - on interchanging (+ and div) and (2 and 4), we get,

(a)  4 div 2 + 3 = 3 ;; or ;; 5=3, which is false.

(b)  2 div 4 +6 =1.5 ;; or ;; 6.5=1.5,  which is false

(c)  2 + 4 div 3 = 4 ; ; or ;; frac {10}{3}=4,  which is false.

(d)  4 div 2 + 6 =8 ;; or ;; 8=8, which is true. 

Hence, the answer is (d).

Sample Questions
(More Questions for each concept available in Login)
Question : 1

Correct the following equation by interchanging two signs (out of +,-,×,÷):

5 × 15 ÷ 7 - 20 + 4 = 77

Right Option : C
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Explanation
Question : 2

Which one of  the four interchanges in signs and numbers would make the given equation correct?

(3 small div4) +2=2

Right Option : A
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Explanation
Question : 3

In each of the following questions, which one of  the four interchanges in signs and numbers would make the given equation correct?

4 small times 6 - 2 = 14

Right Option : C
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Explanation
 
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