For example, if someone got a raise in salary and they were getting paid 80,000 and are now getting paid 85,000 how can you work out what percentage their raise was?
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N. F. Taussig
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Brett
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Percentage change : 100 % times the (Fractional change )
Fractional change : $\frac{85000-80000}{80000}$=$\frac{5000}{80000}$=$\dfrac{1}{16}$
Percentage change : $100\cdot\dfrac{1}{16}$% = $\dfrac{25}{4}$% = $6.25$%
Dheeraj Kumar
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Simple Algebraic intuition : Let the percentage be $x$. Now ask $what\ \%$ of $80000$ gets added to $80000$ to get $85000$. Express it in the form of an equation.
$$\begin{align} 80000+\left(\frac{x}{100}\times80000\right)&=85000 \\ \implies\ \ \ x&=\dfrac{85000-80000}{80000}\times100 \\ &=6.25 \end{align}$$
original / differenceto get the fraction, but I don't quite understand the formula on the second line. What is thedotafter the 100 for? – Brett Dec 16 '14 at 11:32difference / original * 100? – Brett Dec 16 '14 at 12:28$5000per$80000. Percent means per hundred, so to convert that to a percent, we just solvex/100 = 5000/80000for x. – Paul Dec 16 '14 at 15:53x = 100*5000/80000 = 500000/80000 = 50/8 = 6.25– Paul Dec 16 '14 at 15:55