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Mathematical Operations - Interchanging of Symbols

Mathematical Operations - Concepts

Mathematical Operations - Letter Substitution

Mathematical Operations - Interchanging of Symbols

Mathematical Operations - Symbol Substitution

Mathematical Operations - Letter Substitution With Digits

Mathematical Operations - Balancing Inequalities

Mathematical Operations- Deriving Conclusion

Class - 9th Foundation NTSE Subjects

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.

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

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

(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

The given equation becomes correct due to the interchange of two signs. one of the four options specifies the interchange of signs in the equation which when made will make the equation correct. Find the correct option. 5 + 6 $div$ 3 - 12 $times$ 2 = 7
A. $div$ and $times$	B. + and $times$	C. + and $div$	D. + and -
Right Option : A
View Explanation

Question : 2

Which one of the four interchanges in signs and numbers would make the given equation correct? (3 $small div$ 4) +2=2
A. + and $small div$ , 2 and 3	B. + and $small div$ , 2 and 4	C. + and $small div$ ,3 and 4	D. No interchange , 3 and 4
Right Option : A
View 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
A. $small times$ to $small div$ , 2 and 4	B. - to $small div$ , 2 and 6	C. - to +, 2 and 6	D. $small times$ to + , 4 and 6
Right Option : C
View Explanation