Question

$2.7$ is what percent of $18$?
A. $12\% $
B. $13\% $
C. $14\% $
D. $15\% $

Answer 1

Hint: If we want to find $x\% $ of some number $y$ then we can find it by using the formula $\dfrac{x}{{100}} \times y$. To find the required percentage, we will use this formula.

Complete step-by-step solution:
Let us assume that $2.7$ is $x$ percent of $18$. We need to find the value of $x$. First we will write $x$ percent of $18$. That is, $x\% $ of $18 = \dfrac{x}{{100}} \times 18$
$ \Rightarrow x\% $ of $18 = \dfrac{{18x}}{{100}}$
In this problem, it is given that $2.7$ is $x\% $ of $18$. Therefore, we will equate $\dfrac{{18x}}{{100}}$ with $2.7$. Therefore, we can write $\dfrac{{18x}}{{100}} = 2.7 \cdots \cdots \left( 1 \right)$. Now we have the linear equation in one variable $x$.
Let us solve the equation $\left( 1 \right)$ to find the value of $x$. Therefore, we get
$
  18x = 100 \times 2.7 \\
   \Rightarrow 18x = 100 \times \dfrac{{27}}{{10}} \\
   \Rightarrow x = \dfrac{{10 \times 27}}{{18}} \\
   \Rightarrow x = \dfrac{{270}}{{18}} \\
   \Rightarrow x = 15 \\
 $
Therefore, we can say that $15$ percent of $18$ is $2.7$. That is, $15\% $ of $18 = 2.7$.
Therefore, option D is true.

Note: If we want to convert a percentage into decimal then we will divide by $100$. For example, $25\% $ can be written as $\dfrac{{25}}{{100}} = 0.25$ in decimal form. To find the percent of a number, we will multiply that number by the percent and divide the result by $100$. In mathematics, a percentage is the ratio expressed as a fraction of $100$ and it is usually denoted by $\% $ symbol.