A man travels equal distances of his journey at 40 30…

Solution(By ExamCraze Team)

Required average speed,
$$ = {frac{{left( {3 times 40 times 30 times 15} right)}}{{ {left( {40 times 30} right) + left( {40 times 15} right) + left( {30 times 15} right)} }}} $$
$$ = 24,{text{km/hr}}$$

Alternatively
Time taken to traveled $$frac{1}{3}$$ distance of journey with speed 40 kmph,
$$ = frac{{ {frac{1}{3}} }}{{40}} = frac{1}{{120}}$$
Time taken to traveled $$frac{1}{3}$$ distance of journey with speed 30 kmph,
$$ = frac{{ {frac{1}{3}} }}{{30}} = frac{1}{{90}}$$
Time taken to traveled $$frac{1}{3}$$ distance of journey with speed 15 kmph,
$$eqalign{ & = frac{{ {frac{1}{3}} }}{{15}} = frac{1}{{45}} cr & {text{Total time taken}} cr & = {frac{1}{{120}}} + {frac{1}{{90}}} + {frac{1}{{45}}} cr & = frac{{45}}{{1080}} cr & {text{Average speed}} cr & = frac{{{text{Total distance traveled}}}}{{{text{Total time taken}}}} cr & = frac{1}{{ {frac{{45}}{{1080}}} }} cr & = 24,{text{kmph}} cr} $$