Question

Fill in the blanks.
(i) $7\frac{1}{2}\%$ of Rs 1200 = .........
(ii) 240 mL is ......... % of 3 L.
(iii) If x% of 35 is 42, then x = .........
(iv) $\frac{12}{5}$ = .........%.
(v) 120 = (.........)% of 80.

Answer 1

$\left(\mathrm{i}\right)7\frac{1}{2}\%\mathrm{of}\mathrm{Rs}1200=\left(\frac{15}{2}\%\mathrm{of}\mathrm{Rs}1200\right)$
$$\begin{gathered} =\mathrm{Rs}\left(\frac{15}{2}\times \frac{1}{100}\times 1200\right) \\ =\mathrm{Rs}90 \end{gathered}$$
$\mathrm{Hence},7\frac{1}{2}\%\mathrm{of}\mathrm{Rs}1200=\mathrm{Rs}90$

$$\begin{gathered} \left(\mathrm{ii}\right)\mathrm{Required}\mathrm{percentage}=\left(\frac{240}{3\times 1000}\times 100\right)\%=8\% \\ \mathrm{Hence},240\mathrm{ml}\mathrm{is}8\%\mathrm{of}3\mathrm{L}. \end{gathered}$$

$$\begin{gathered} \left(\mathrm{iii}\right)\left(\mathrm{x}\%\mathrm{of}35\right)=42 \\ \Rightarrow \left(35\times \frac{\mathrm{x}}{100}\right)=42 \\ \Rightarrow \frac{35\mathrm{x}}{100}=42 \\ \Rightarrow \mathrm{x}=\left(42\times \frac{100}{35}\right) \\ \Rightarrow \mathrm{x}=120\% \\ \therefore \mathrm{If}\mathrm{x}\%\mathrm{of}35\mathrm{is}42,\mathrm{then}\mathrm{x}=120\%. \end{gathered}$$

$$\begin{gathered} \left(\mathrm{iv}\right)\left(\frac{12}{5}\times 100\right)\%=240\% \\ \mathrm{Hence},\frac{12}{5}=240\% \end{gathered}$$

$$\begin{gathered} \left(v\right)\mathrm{Let}\mathrm{the}\mathrm{required}\mathrm{number}\mathrm{be}\mathrm{x}.\mathrm{Then},\mathrm{we}\mathrm{have}: \\ 120=x\%of80 \\ \Rightarrow \left(80\times \frac{x}{100}\right)=120 \\ \Rightarrow \frac{80x}{100}=120 \\ \Rightarrow x=\left(120\times \frac{100}{80}\right) \\ \Rightarrow x=150\% \\ \therefore 120=150\%\mathbf{}of80 \end{gathered}$$