Mathematical Operations Questions and Answers

Answer: D

Correct answer: 36 -6 + 3 × 5 ÷ 3 = 74

Substituting in this option gives \[ 36 \times 6 \div 3 + 5 - 3. \] Multiplication and division first, left to right: \( 36\times6 = 216 \), then \( 216\div3 = 72 \). Then \( 72 + 5 - 3 = 74 \), which matches. The other three options do not balance once their signs are replaced.

Answer: C

Correct answer: 5 ÷ 3 - 25 + 20 = 20 x 39

The substitutions are \( = \to \div \), \( + \to - \), \( \times \to = \), \( - \to + \) and \( \div \to \times \). Note that \( \times \) becomes the equals sign, so it marks where the two sides of the equation meet.

Decoding the correct option gives \( 5 \times 3 + 25 - 20 \div 20 = 39 \), and by BODMAS \[ 15 + 25 - 1 = 39 \] which is true. For contrast, \( 96 \div 2\ \text{x}\ 6 \div 105 + 1 \) decodes to \( 192 = 630 - 1 \), which is false.

Answer: D

Correct answer: 14

The code swaps the symbols: \( - \to + \), \( + \to \times \), \( \times \to \div \), \( \div \to - \). So \( 2 - 12 + 10 \times 5 \div 12 \) is read as \( 2 + 12 \times 10 \div 5 - 12 \).

Applying BODMAS to the decoded expression: \[ 2 + 12 \times 10 \div 5 - 12 = 2 + 24 - 12 = \mathbf{14} \]

Answer: B

Correct answer: 30

Substituting gives \[ 28 \div 7 \times 8 - 6 + 4. \] Division and multiplication first, left to right: \( 28\div7 = 4 \), \( 4\times8 = 32 \). Then \( 32 - 6 + 4 = 30 \).

Answer: B

Correct answer: 235

Replacing the symbols gives \( 25 \times 10 - 240 \div 16 \), and by the usual order \[ 250 - 15 = \mathbf{235} \]

Answer: D

Correct answer: None of these

Substituting gives \[ 18 + 12 \div 6 \times 2 - 5. \] Division and multiplication come first, left to right: \( 12\div6 = 2 \), then \( 2\times2 = 4 \). So the value is \( 18 + 4 - 5 = 17 \), which is not among the three figures offered.

Answer: C

Correct answer: + and –, 3 and 5

Interchanging the two signs and the numbers 3 and 5 turns \( 3 + 5 - 2 \) into \( 5 - 3 + 2 \), which is 4 as required. Swapping 2 with 3 instead gives \( 2 - 5 + 3 = 0 \), and swapping 2 with 5 gives \( 3 - 2 + 5 = 6 \) - so only the third interchange works.

Answer: D

Correct answer: 80

The rule is to take five from the first number and double the result: \( (25-5)\times2 = 40 \) and \( (35-5)\times2 = 60 \). So \[ (45-5) \times 2 = \mathbf{80} \]

Answer: C

Correct answer: 12

\( -4 - (-10) = -4 + 10 = 6 \) and \( -10 - (-4) = -10 + 4 = -6 \). The first exceeds the second by \[ 6 - (-6) = \mathbf{12} \]

Answer: D

Correct answer: None of these

Substituting turns the expression into one whose value falls outside every figure offered, so the answer is none of them. The stem’s list of definitions has been damaged - one sign appears against two different operations - but on any consistent reading of it the result is a value the three numbered options do not contain.