Jack and Jerry can complete a job in 2 hours when working together.If Jack requires 6 hours to finish the job alone,how many hours does Jerry need to finish the job alone?
1/2 = 1/6 + 1/x
Just by inspection, we can see that x=3, so it takes Jerry 3 hours to do the job.
why use 1/2 , because 2 hours half
Read up on these work problems. If Jack can do the job in 6 hours, he does 1/6 of the job in an hour.
If together they can do the job in 2 hours, they can do 1/2 the job in one hour.
So, you need to add up how much each guy can do in one hour, and the sum is what fraction of the job gets done in one hour.
That is why, if you have several people all working together, with completion times of x,y,z,... hours, the equation to solve to find the time it takes for them to do it together (N hours) is
1/x + 1/y + 1/z + ... = 1/N
If three exterior angles of a quadrilateral measure 125 degree, 85 degree,100 degree, find the measure of the interior angles of a quadrilateral?
To find out how many hours Jerry needs to finish the job alone, we can use the concept of work rates.
Let's assume that Jack's work rate is J (the amount of job completed by Jack in one hour) and Jerry's work rate is W (the amount of job completed by Jerry in one hour).
We are given that when Jack and Jerry work together, they can complete the job in 2 hours. So their combined work rate is 1 job / 2 hours = 1/2.
Also, we are given that Jack requires 6 hours to finish the job alone, so his work rate is 1 job / 6 hours = 1/6.
Since we know the combined work rate of Jack and Jerry, we can subtract Jack's work rate from it to find Jerry's work rate:
Combined work rate - Jack's work rate = Jerry's work rate
1/2 - 1/6 = Jerry's work rate
3/6 - 1/6 = Jerry's work rate
2/6 = Jerry's work rate
1/3 = Jerry's work rate
Therefore, Jerry's work rate is 1/3, meaning he can complete 1/3 of the job in one hour.
To find out how many hours Jerry needs to finish the job alone, we can use his work rate:
1 job / Jerry's work rate = Number of hours Jerry needs
Plugging in the value of Jerry's work rate:
1 job / (1/3) = Number of hours Jerry needs
1 job * 3 = Number of hours Jerry needs
3 = Number of hours Jerry needs
Therefore, Jerry needs 3 hours to finish the job alone.