Question

What is \[40\% {\text{ of }}\left[ {100 - 20\% {\text{ of }}300} \right]\] is equal to
A. 20
B. 16
C. 140
D. 64

Answer 1

Hint: We will solve the given expression by considering multiplication. The number written in the form of $x\% $ is $\dfrac{x}{{100}}$ in fractional form. Write the given expression as \[\dfrac{{40}}{{100}} \times \left[ {100 - \dfrac{{20}}{{100}} \times 300} \right]\] and hence simplify the expression.

Complete step-by-step answer:
We will first solve the brackets of the given expression.
Here, \[20\% {\text{ of }}300\] is equivalent to \[20\% \times 300\]
Of is considered as multiplication.
And $x\% $ in fractional form is written as $\dfrac{x}{{100}}$
Then the gives expression is written as
$
  40\% \times \left[ {100 - 20 \times 300} \right] \\
   \Rightarrow \dfrac{{40}}{{100}} \times \left[ {100 - \dfrac{{20}}{{100}} \times 300} \right] \\
$
On simplifying the above expression as,
$
  \dfrac{{40}}{{100}} \times \left[ {\dfrac{{100\left( {100} \right) - 20 \times 300}}{{100}}} \right] \\
   \Rightarrow \dfrac{{40}}{{100}} \times \left[ {\dfrac{{100\left( {100} \right) - 20 \times 300}}{{100}}} \right] \\
$
$
   \Rightarrow \dfrac{{40}}{{100}} \times \left[ {\dfrac{{10000 - 6000}}{{100}}} \right] \\
   \Rightarrow \dfrac{{40}}{{100}} \times \left[ {\dfrac{{4000}}{{100}}} \right] \\
   \Rightarrow 4 \times 4 = 16 \\
$
Hence, option B is correct.

Note: Percentage is a number or ratio that represents a fraction of 100. We can express the percentage form in fraction form or in decimal form. Also, while solving the question, we must follow the BODMAS rule.