Show an equation and a solution for the problem. At the coal mine, it takes the older conveyor belt 20 hours to move one day's coal output. The new belt can do it in 15 hours. If the old belt began to move the day's output and the new belt started as well an hour later, how long would it take to move it? Round to the nearest tenth.

Question

Show an equation and a solution for the problem.  At the coal mine, it takes the older conveyor belt 20 hours to move one day's coal output.  The new belt can do it in 15 hours.  If the old belt began to move the day's output and the new belt started as well an hour later, how long would it take to move it?  Round to the nearest tenth.

anonymous · Answer

9.143 hrs

anonymous · Answer

Old belt can complete 1/20 th of work in one hour
and new belt can complete 1/15 th of the work in 1 hour
thus both can complete $$\frac{1}{20}+\frac{1}{15} = (\frac{7}{60})$$
in one hour and as old belt started one hour before so
work left = $$1- \frac{1}{20} = \frac{19}{20}$$

there fore together the two belts can complete the remaining work in 
$$\frac{19}{20}\times \frac{60}{7}  = \frac{57}{7} hrs$$

therefore total time to complete the work = $$1 + \frac{57}{7} = \frac{64}{7} = 9.142 hrs$$

saifoo.khan · Answer

sheg is helping people these days!

anonymous · Answer

b4 i dint used to help

saifoo.khan · Answer

Right.

anonymous · Answer

fir mein kya karta tha mere bhai????

saifoo.khan · Answer

Tafreeiyan! ;)

anonymous · Answer

haahahhaa.........achha hai boss

anonymous · Answer

by d way mujhe iska matlab nahi pata hai!!!

saifoo.khan · Answer

LOL. great.