The ratio 4

The ratio of two number is 5:4 if 40% of the first number is 12, what will be 50% of the second number?

Correct answer:

x =  12

Step-by-step explanation:

$$\begin{gathered} a:b=5:4 \\ {p}_1=40\mathrm{\%}={\displaystyle \frac{40}{100}}=0.4 \\ {p}_1\cdot a=12 \\ 0.4\cdot a=12 \\ 0.4a=12 \\ a=30 \\ b=a\cdot {\displaystyle \frac{4}{5}}=30\cdot {\displaystyle \frac{4}{5}}=24 \\ {p}_2=50\mathrm{\%}={\displaystyle \frac{50}{100}}=0.5 \\ x=p_2\cdot b=0.5\cdot 24=12 \end{gathered}$$

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