A car covers 60 km with a uniform speed of 120kmph and the next 60 km with a uniform speed of 80kmph. The total time taken by the car is                             

Given that a car covers s = 60km

V = 120kmph     $\left(\because \text{t}=\frac{\text{s}}{\text{v}}\right)$

Time taken ${\text{t}}_{\text{1}}=\frac{60}{120}\text{hours}$

Next covered s = 60km

v = 80kmph

Time taken ${\text{t}}_{\text{2}}=\frac{60}{80}\text{hours}\left(\because \text{t}=\frac{\text{s}}{\text{v}}\right)$

Total time taken $\text{t}={\text{t}}_{\text{1}}+{\text{t}}_{\text{2}}$  

$\text{t}=\frac{60}{120}\text{hours}+\frac{60}{80}\text{hours}$

$\text{t}=\frac{60\times 2+3\times 60}{240}\text{hours}$

$\text{t}=\frac{120+180}{240}\text{hr}$

$\text{t}=\frac{300}{240}\times 60\min \left(\because 1\text{hr}=60\min \right)$

$\text{t}=\frac{300}{240}\times 60\min$

t = 75 min