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Question

Two-fifth of seven-seventeenth of three-fifth of a number is 84. Find 40% of that number.

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
340

Fractional Calculation: Finding 40% of a Number

Let the unknown number be represented by '$x$'.

Step 1: Formulate the Equation

The problem states that "Two-fifth of seven-seventeenth of three-fifth of a number is 84". This translates to the following equation:

$ \frac{2}{5} \times \frac{7}{17} \times \frac{3}{5} \times x = 84 $

Step 2: Calculate the Product of Fractions

Multiply the given fractions together:

$ \frac{2 \times 7 \times 3}{5 \times 17 \times 5} = \frac{42}{425} $

The equation simplifies to:

$ \frac{42}{425} \times x = 84 $

Step 3: Solve for the Number (x)

To isolate '$x$', rearrange the equation:

$ x = 84 \times \frac{425}{42} $

Perform the calculation:

$ x = 2 \times 425 $

$ x = 850 $

The value of the number is 850.

Step 4: Calculate 40% of the Number

The final step is to find 40% of the number '$x$' (which is 850).

Convert 40% to a decimal or fraction: $40\% = \frac{40}{100} = 0.4$.

Calculate 40% of 850:

$ 0.4 \times 850 $

Alternatively, using fractions:

$ \frac{40}{100} \times 850 = \frac{2}{5} \times 850 $

$ = \frac{2 \times 850}{5} = 2 \times 170 $

$ = 340 $

Thus, 40% of the number is 340.

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    can be written in the form of:
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  3. Four persons A, B, C and D completed a task in $\frac{2}{3} \text{ h}, \frac{3}{4} \text{ h}, \frac{4}{5} \text{ h}$ and $\frac{1}{5} \text{ h}$ respectively. Who among the following took the highest amount of time to complete the task?
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Important Questions from Fractions

  1. 5 \(\frac{3}{4}\) + x + 2  \(\frac{1}{2}\) = 10  \(\frac{1}{8}\) Find the value of x.

  2. Simplify the expression 441 ÷  \(\left[270 \div \frac{3}{7}+\left(17\div \frac{1}{3}\right)-\left(8\frac{1}{2}-\frac{5}{2}\right)\right]\)

  3. Number 0.232323 can be written in rational form as:

  4. Solve: \(\frac{1}{2}\)  [{-2(2 + 3)*20}/2]

  5. Match the following.

    Column I

    Column II

    a.

    Equivalent fraction of \(\frac{7}{12}\)  is  

    i.

    Proper fraction

    b.

    Equivalent fraction of  \(\frac{9}{15}\)  is

    ii.

    Improper fraction

    c.

    \(\frac{7}{11}\)  is

    iii.

    \(\frac{21}{36}\)

    d.

    \(\frac{19}{5}\)  is

    iv.

    \(\frac{3}{5}\)

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