Question

A can do a work in 15 days. B in 25 days and C in 30 days. How long will they take to do the work if they work together?

Answer 1

Answer:

it will take

$7 \frac{1}{7} days$

Step-by-step explanation:

time taken by A=15days

work done by A in 1 day=1/15

time taken by B=25 days

work done by B in 1 day=1/25

time taken by C=30 days

work done by C in 1 day=1/30

work done in 1 day if they work together =

$\frac{1}{15} + \frac{1}{25} + \frac{1}{30} = \frac{10 + 6 + 5}{150} = \frac{21}{150}$

so to find the work done when time is given we simply do

$\frac{time}{1} = \frac{1}{time}$

in similar manner to find time

$\frac{1}{work} = \frac{work}{1}$

so total work in 1 day=21/150

total time=

$\frac{150}{21} = 7 \frac{3}{21} = 7 \frac{1}{7} days$