Question

On one day a rickshaw puller earned Rs 80. Out of his earnings he spent Rs on tea and snacks. Rs on food and Rs on repairs of the rickshaw. How much did he save on that day?

Answer 1

Money saved by the rickshaw puller = Total money earned - (Earnings spent on tea and snacks + Earnings spent on food + Earnings spent on repairs)
$$\begin{gathered} =80-\left(13\frac{3}{5}+25\frac{1}{2}+4\frac{2}{5}\right) \\ =80-\left(\left(13+\frac{3}{5}\right)+\left(25+\frac{1}{2}\right)+\left(4+\frac{2}{5}\right)\right) \\ =80-\left(\frac{68}{5}+\frac{51}{2}+\frac{22}{5}\right) \end{gathered}$$

$$\begin{gathered} \mathrm{Now}, \\ \frac{68}{5}+\frac{51}{2}+\frac{22}{5}=\frac{\left(68\times 2\right)+\left(51\times 5\right)+\left(22\times 2\right)}{10} \\ =\frac{136+255+44}{10} \\ =\frac{435}{10} \\ =\frac{87}{2} \end{gathered}$$

∴$\frac{68}{5}+\frac{51}{2}+\frac{22}{5}=\frac{87}{2}$
Money saved by the rickshaw puller $=80-\frac{87}{2}$
$$\begin{gathered} =80+\left(\mathrm{Additive}\mathrm{inverse}\mathrm{of}\frac{87}{2}\right) \\ =\frac{160-87}{2} \\ =\frac{73}{2} \\ =\mathrm{Rs}36\frac{1}{2} \end{gathered}$$
Therefore, the amount of money saved by the rickshaw puller is Rs $36\frac{1}{2}$.