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Percentage

In this chapter, we will be discussing the below-mentioned topics in detail:

  • Fractions, Ratio, Decimals and Percentage
  • Convert a non-integer percentage to fraction/ decimal and vice versa
  • Percentages greater than \(100\%\) or less than \(1\%\)
  • Percentage of quantities 
    • Percentage of a quantity 
    • Express one quantity as a percentage of another quantity
    • Compare two quantities by percentage
  • Percentage change

Fractions, Ratio, Decimals and Percentage

Let’s understand this with the help of some examples:

Fractions Ratio Percentage Decimals
\(\begin{align} \frac{2}{5} \end{align}\) \(\mathrm{2:5}\) \(\begin{align} \frac{2}{5} \times 100 = 40\% \end{align}\) \(\begin{align*} 40\% &= \frac{40}{100}\\ \\       &= 0.4 \end{align*}\)
\(\begin{align} 25\% &= \frac{25}{100}\\\\  &= \frac{1}{4} \end{align}\) \(\mathrm{1:4}\) \(\mathrm{25\%}\) \(\mathrm{0.25}\)
\(\begin{align} \frac{90}{100} = \frac{9}{10} \end{align}\) \(9:10\) \(\begin{align} 0.9 \times 100\% = 90\% \end{align}\) \(\mathrm{0.9}\)

 

Percentages Greater Than 100% or Less Than 1%

Let’s understand this with the help of some examples:

Question 1:

Without using a calculator, express each of the following percentages as a fraction.

  1. \(105\%\)
  2. \(0.04\%\) 

Solution: 

  1.  

\(\begin{align*} 105\% &= \frac{105}{100}\\ &= \frac{21}{20}\\ &= 1\frac{1}{20} \end{align*}\)

 

  1.  

\(\begin{align*} 0.04\% &= \frac{0.04 × 100}{100 × 100}\\ &= \frac{4}{10000}\\ &= \frac{1}{2500} \end{align*}\)

 

Question 2:

Without using a calculator, express each of the following percentages as a decimal.

  1. \(274\%\)
  2. \(0.38\%\)

Solution: 

  1.  

\(\begin{align*} 274\% &=  \frac{274}{100}\\ \\                   &= 2.74 \\ \\ \end{align*}\)

  1.  

\(\begin{align*} 0.38\% &= \frac{0.38}{100}\\ \\                     &= 0.0038\\ \end{align*}\)

 

Percentage Of A Quantity

Let’s understand this with the help of some examples:

Question 3:

A box contains \(60\) balls, of which \(16\) are red.

  1. If \(40\%\) of the balls are green, find the number of green balls.
  2. The rest of the balls in the box are yellow.

If \(70\%\) of the yellow balls are removed, find the number of yellow balls left.

Solution: 

  1. Number of green balls\(\begin{align}\\[2ex] &= \frac{40}{100} \times 60\\[2ex] &=24 \text{ balls} \end{align}\)

OR
Number of green balls\(\begin{align}\\[2ex] &= 0.4 \times 60\\[2ex] &=24 \text{ balls} \end{align}\)

  1. Number of yellow balls at first\(\begin{align}\\[2ex] &= 60 \;– 16 \;– 24\\[2ex] &=20 \end{align} \)
    Number of yellow balls remaining\(\begin{align}\\[2ex] &= \frac{30}{100} \times 20\\[2ex] &=6 \text{ balls} \end{align}\)

OR
Number of yellow balls remaining\(\begin{align}\\[2ex] &= 0.3 \times 20\\[2ex] &=6 \text{ balls} \end{align}\) \(\)

 

Comparing Two Quantities By Percentage

Let’s understand this with the help of some examples:

Question 4:

Shop A sold \(225\) out of \(1000\) vinyl records in January. Shop B sold \(400\) out of \(1500\) vinyl records in the same month. Which shop had a higher proportion of sales in January?

Solution: 

Percentage of sales by Shop A\(\begin{align}\\[2ex] &= \frac{225}{1000} \times 100\\[2ex] &=22.5\% \end{align}\)
Percentage of sales by Shop A\(\begin{align}\\[4ex] &= \frac{400}{1500} \times 100\\[2ex] &=26\frac{2}{3}\% \end{align}\)

Shop \(B\) had a higher proportion of sales in January.
 

Continue Learning
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Basic Algebra And Algebraic Manipulation 1 Approximation And Estimation
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