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Mathematical Operations Questions and Answers

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71.

In a certain code language, 'x' represents '+', '÷' represents 'x', '-' represents '÷' and '+' represents '-'. Find out the answer to the following question.

5 + 10 x 21 ÷ 5 - 15 = ?

Answer: B

Correct answer: 2

Replacing the symbols gives \( 5 - 10 + 21 \times 5 \div 15 \), and by the usual order \[ 5 - 10 + 7 = \mathbf{2} \]

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72.

What approximate value will come in place of question mark (?) in the following question ?

 (49.001)²  = ?

Answer: B

Correct answer: 2400

\( 49^2 = 2401 \), and 49.001 differs from 49 by so little that the square is still about 2401. To the nearest figure offered that is 2400.

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73.

A sum of Rs.1890 has to be used to give 9 prizes to the customers of a super market for their overall academic purchases. If each prize is Rs.30 less than its preceding price, what is the least value of the price ?

Answer: A

Let the least value of the prize = Rs. x

Then the next value of the prize is x+30 , x+60, x+90, ....x+240.

Given total amount of cash prizes = Rs.1890

--> x + (x+30) + (x+60) + (x+90) + ....+ (x+240) = 1890

--> 9x + (30 + 60 + 90 + 120 + 150 + 180 + 210 + 240) = 1890

--> 9x + 30(1 + 2 + 3 + 4....+ 8) = 1890

--> 9x + 30(36) = 1890

--> 9x = 810 --> x=90

Hence the least value of the prize x=90

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Answer: C

Correct answer: 3 > 2 < 4 x 8 + 4 < 2

This item cannot be worked as it stands: the stem breaks off part way through the list of definitions, so only the meaning of the first symbol survives. Without the full set of substitutions the four expressions cannot be evaluated or compared.

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75.

If L stands for +, M stands for -, N stands for ×, P stands for ÷, then 14 N 10 L 42 P 2 M 8 = ?

Answer: A

Correct answer: 153

Substituting gives \[ 14 \times 10 + 42 \div 2 - 8 = 140 + 21 - 8 = 153. \] Both the multiplication and the division are completed before anything is added or subtracted, which is what keeps the two products separate rather than running them into one another.

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76.

Can you Solve 7 + 7 ÷ 7 + 7 x 7 + 7 − 7 ÷ 7 + 7 x 7

Answer: A

Correct answer: 112

Doing the divisions and multiplications first turns the expression into \( 7 + 1 + 49 + 7 - 1 + 49 \), which adds up to \[ \mathbf{112} \]

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77.

The following equation is incorrect. Which two signs should be interchanged to correct the equation?

10 x 4 + 5 - 30 ÷ 6 = 31

Answer: A

Correct answer: x and -

Exchanging × and − gives \( 10 - 4 + 5 \times 30 \div 6 \), which works out as \[ 10 - 4 + 25 = \mathbf{31} \]

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78.

3 x 3 + 3 - 3 + 3 = ?

Answer: B

Correct answer: 12

Multiplication comes first, so the expression is \( 9 + 3 - 3 + 3 \), which is \[ \mathbf{12} \]

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79.

If 19 (36) 13 and 37 (81) 28, then what is the value of 'A' in 43 (A) 38?

Answer: C

Correct answer: 25

The number in brackets is the square of the difference of the outer two: \( (19-13)^2 = 36 \) and \( (37-28)^2 = 81 \). So \[ A = (43-38)^2 = \mathbf{25} \]

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80.

If (3)² @ 1 * 7 = 98 and (4)² @ 2 * 16 = 178, then (5)² @ 3 * 9 = ?

Answer: B

Correct answer: 262

The two operators are not arithmetic in the usual sense. Square the bracketed number, then \( @ \) writes the next number immediately after it (digits joined, not added), and \( * \) adds the final number.

Checking both worked examples: \( (3)^2 = 9 \), joined with 1 gives 91, and \( 91 + 7 = 98 \). \( (4)^2 = 16 \), joined with 2 gives 162, and \( 162 + 16 = 178 \).

So \( (5)^2 = 25 \), joined with 3 gives 253, and \[ 253 + 9 = \mathbf{262} \] The option 253 is the value before the last addition, offered as a distractor.

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