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Question

Select the option that can replace the question mark (?) in the following equation.

2 + 5 ÷ [5 + 8 ÷  \(\left(1+\frac{1}{3}\right)\) - 1 ] = ?

This question was previously asked in
RRB ALP 2018 CBT 2 Fitter Question Paper (21-Jan-2019) (Shift 3)
The correct answer is \(\frac{5}{2}\)

Simplifying Mathematical Expressions with BODMAS/PEMDAS

To solve the given mathematical expression, we need to follow the order of operations. A common acronym used for remembering the order is BODMAS or PEMDAS.

  • B/P: Brackets or Parentheses (solve operations inside these first)
  • O/E: Orders or Exponents (powers, square roots, etc.)
  • D/M: Division or Multiplication (from left to right)
  • A/S: Addition or Subtraction (from left to right)

The expression is: \(2 + 5 \div [5 + 8 \div\left(1+\frac{1}{3}\right) - 1 ]\)

Step-by-Step Calculation

Let's break down the calculation according to the order of operations.

Step 1: Solve the operation inside the innermost parentheses \(\left(1+\frac{1}{3}\right)\)

First, calculate the sum inside the small brackets:

\(1 + \frac{1}{3} = \frac{3}{3} + \frac{1}{3} = \frac{3+1}{3} = \frac{4}{3}\)

The expression now becomes:

\(2 + 5 \div [5 + 8 \div \left(\frac{4}{3}\right) - 1 ]\)

Step 2: Solve the division inside the square brackets \([5 + 8 \div \left(\frac{4}{3}\right) - 1 ]\)

Next, perform the division inside the square brackets:

\(8 \div \left(\frac{4}{3}\right) = 8 \times \frac{3}{4}\)

Multiply 8 by the reciprocal of \(\frac{4}{3}\):

\(8 \times \frac{3}{4} = \frac{8 \times 3}{4} = \frac{24}{4} = 6\)

The expression now becomes:

\(2 + 5 \div [5 + 6 - 1 ]\)

Step 3: Solve the operations inside the square brackets \([5 + 6 - 1 ]\)

Perform the addition and subtraction from left to right inside the square brackets:

\(5 + 6 - 1 = 11 - 1 = 10\)

The expression now becomes:

\(2 + 5 \div [10]\)

or simply

\(2 + 5 \div 10\)

Step 4: Perform the remaining division

Now, perform the division:

\(5 \div 10 = \frac{5}{10} = \frac{1}{2}\)

The expression now becomes:

\(2 + \frac{1}{2}\)

Step 5: Perform the final addition

Finally, add the numbers:

\(2 + \frac{1}{2} = \frac{4}{2} + \frac{1}{2} = \frac{4+1}{2} = \frac{5}{2}\)

The value of the expression is \(\frac{5}{2}\).

Summary of Calculation Steps

Step Operation Calculation Expression Becomes
1 Innermost Parentheses \(1+\frac{1}{3} = \frac{4}{3}\) \(2 + 5 \div [5 + 8 \div \frac{4}{3} - 1 ]\)
2 Division inside Brackets \(8 \div \frac{4}{3} = 6\) \(2 + 5 \div [5 + 6 - 1 ]\)
3 Brackets Operations \(5 + 6 - 1 = 10\) \(2 + 5 \div 10\)
4 Division \(5 \div 10 = \frac{1}{2}\) \(2 + \frac{1}{2}\)
5 Addition \(2 + \frac{1}{2} = \frac{5}{2}\) \(\frac{5}{2}\)

Thus, the result of the expression is \(\frac{5}{2}\).

Revision Table: Order of Operations

Order Operation Type Notes
1st Parentheses / Brackets Work from innermost to outermost.
2nd Exponents / Orders Calculate powers and roots.
3rd Multiplication and Division Perform from left to right.
4th Addition and Subtraction Perform from left to right.

Additional Information: Fractions and Mixed Numbers

In this problem, we encountered a mixed number operation (\(1 + \frac{1}{3}\)). A mixed number combines a whole number and a fraction. To perform arithmetic with mixed numbers, it's often easiest to convert them into improper fractions.

  • A number like \(1\) can be written as a fraction with any denominator (e.g., \(\frac{1}{1}\), \(\frac{2}{2}\), \(\frac{3}{3}\)). To add it to \(\frac{1}{3}\), we wrote \(1\) as \(\frac{3}{3}\).
  • An improper fraction is one where the numerator is greater than or equal to the denominator (e.g., \(\frac{4}{3}\)).

We also performed division by a fraction. Dividing by a fraction is the same as multiplying by its reciprocal. The reciprocal of \(\frac{4}{3}\) is \(\frac{3}{4}\).

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Similar Questions

  1. What is the fraction form of $87\frac{1}{2}$ %?

  2. Which of the following is true?

  3. Which of the fractions given below, when added to 5/8, give 1?

  4. By what number should \(10\frac{2}{3}\) be divided to obtain 20?

  5. 23 × 31 = 713. How much is 0.0713 ÷ 3.1?

  6. A fraction, when taken away from \(\frac{1}{3}\)  gives  \(\frac{1}{12}\)  The fraction is:

  7. Tapan, Ravi and Trisha shared a cake. Tapan had 1/3 of it, Trisha had 1/2 of it and Ravi had the rest. What was Ravi’s share of the cake?

  8. Tapan, Ravi, and Trisha shared a cake. Tapan had 1/4 of it, Trisha had 2/3 of it and Ravi had the rest. What was Ravi’s share of the cake?

  9. What is the fraction which, when taken away from 1/2, gives 2/3?

  10. A television show lasted for \(4\frac{2}{3}\) hours. If 1/5th of the total time was spent on advertisements, what was the actual duration of the television show?


Important Questions from Fractions

  1. If three-fifths of a number is 54, what is two-ninth of it?

  2. Sunila had \(9\frac{1}{4}\) kg of flour to make bread with. If the recipe says that she needs  \(1\frac{1}{8}\) kg to make one loaf of bread, how many loafs can she make? Estimate to the nearest whole number.

  3. The value of \(\frac{{11}}{5} - \left( {\frac{2}{3}of\frac{3}{5} - \frac{1}{5}} \right) + \left( {\frac{6}{5} \div \frac{4}{5}} \right)\) is:

  4. In his career, a tennis player won 5 matches lost 12 matches and had 3 matches as draw. The fraction of the match he lost in his career is:

  5. Simplify:

    \(62\div 5 - \left(\frac{8}{9}\times \frac{18}{7}\right)\times \frac{7}{5}+\frac{5}{4}\times \frac{16}{25}\)

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