You don't need a formula. You need to understand where the answer comes from.
If you understand where the answer comes from, you can write your own formula.
If you don't, then a formula can be dangerous in your hands.
-- Sally can paint 1/4 of the house in an hour.
-- John can paint 1/6 of the same house in an hour.
-- If they work together, then can paint (1/4 + 1/6) = 5/12 of the house in an hour.
-- If they paint 5/12 of the house in an hour, then it takes them 12/5 hours to
finish the job, or 2.4 hours, or 2hours 24minutes.
Well, OK. Here's the formula:
S = number of hours it takes Sally
J = number of hours it takes John
Number of hours it takes them working together = 1 / (1/S + 1/J)
It would take them 4 hours to paint the house together.
Less than two hours.
~1.9 hours
It will take about 11.1 hours for the two of them to complete the roofing of the house.
Sally does a quarter of the house in an hour, John does one-sixth, so together they would do 5/12 in an hour, thus it would take 12/5 hours ie 2 hrs 24 min in theory. In practice, because of arguments it would probably take three hours plus!
It would take them 4 hours to paint the house together.
It will take Sally and John 2.4 hours to paint the house together. This can be calculated by using the formula 1/4 + 1/6 = 5/12, which means they can paint 5/12 of the house per hour together. To find the time it takes to paint the whole house, you can divide 1 (the whole house) by 5/12, which equals 2.4 hours.
Less than two hours.
~1.9 hours
if sally can paint a house in 4 hours and john can paint the same house in 6 hours, how long will it take for them to paint the house together?
The way you calculate this (assuming that both work at constant speed) is:* Calculate what part of the house each person can paint in an hour. * Add both fractions together, to calculate what part of the house you can paint together. * Take the reciprocal of this last result, to calculate the number of hours.
It will take about 11.1 hours for the two of them to complete the roofing of the house.
About 12.5 hours if they just work. Since there are now two people working, the gab factor could increase that to 40 hours.
Sally does a quarter of the house in an hour, John does one-sixth, so together they would do 5/12 in an hour, thus it would take 12/5 hours ie 2 hrs 24 min in theory. In practice, because of arguments it would probably take three hours plus!
Sally does 1 job in 4 hours ===> 1/4th of the job per hour.John does 1 job in 6 hours ===> 1/6th of the job per hour.Working together, they do (1/4 + 1/6) = (3/12 + 2/12) = 5/12 job per hour.The job takes 12/5 = 2.4 hours = 2hours24minutes to complete.
Joe can paint the house in 3 hours so Joe paints 1/3 house in an hour. Similarly, Sam paint 1/5 of the house in one hour. So together (assuming no synergy) they paint 1/3 + 1/5 = 8/15 of the house in an hour. So they take 15/8 = 1 + 7/8 = 1.875 days to paint it.
After Hours at the London House was created in 1959.