Fill in the blanks.

Solution:

(i) $7 \frac{1}{2} \%$ of Rs $1200=\left(\frac{15}{2} \%\right.$ of Rs 1200$)$

$=\operatorname{Rs}\left(\frac{15}{2} \times \frac{1}{100} \times 1200\right)$

$=\operatorname{Rs} 90$

Hence, $7 \frac{1}{2} \%$ of Rs $1200=$ Rs 90

(ii) Required percentage $=\left(\frac{240}{3 \times 1000} \times 100\right) \%=8 \%$

Hence, $240 \mathrm{ml}$ is $8 \%$ of $3 \mathrm{~L}$.

(iii) $(\mathrm{x} \%$ of 35$)=42$

$\Rightarrow\left(35 \times \frac{x}{100}\right)=42$

$\Rightarrow \frac{35 x}{100}=42$

$\Rightarrow x=\left(42 \times \frac{100}{35}\right)$

$\Rightarrow x=120 \%$

$\therefore$ If $\mathrm{x} \%$ of 35 is 42, then $\mathrm{x}=120 \%$.

(iv) $\left(\frac{12}{5} \times 100\right) \%=240 \%$

Hence, $\frac{12}{5}=240 \%$

(v) Let the required number be $\mathrm{x}$. Then, we have:

$120=x \%$ of 80

$\Rightarrow\left(80 \times \frac{x}{100}\right)=120$

$\quad \Rightarrow \frac{80 x}{100}=120$

$\quad \Rightarrow x=\left(120 \times \frac{100}{80}\right)$

$\quad \Rightarrow x=150 \%$

$\therefore 120=150 \%$ of 80