Rosa can eat 32 rosogollas in one hour. Her sister Lila needs three hours to eat the same number. How much time will they take to eat 32 rosogollas together ?

Number of rosogollas eaten by Rosa in 1 minute = $$\frac{{32}}{{60}}$$
Number of rosogollas eaten by Lila in 1 minute =$$\frac{{32}}{{180}}$$
Number of rosogollas eaten by Rosa and Lila together in 1 minute
$$\eqalign{ & {\text{ = }}\left( {\frac{{32}}{{60}} + \frac{{32}}{{180}}} \right) \cr & {\text{ = }}\frac{{128}}{{180}} \cr & \therefore {\text{Required time}} \cr & = \left( {32 \div \frac{{128}}{{180}}} \right){\text{minutes}} \cr & = \left( {\frac{{32 \times 180}}{{128}}} \right){\text{minutes}} \cr & = {\text{ 45 minutes}} \cr} $$