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What is the answer to this math problem?
Please explain how.
Farmer A can plow a certain field in 6 hours by herself. Working together with Farmer B, it takes them 4.5 hours. How long would it take Farmer B to plow the field on his own?
The answer given is 18, but I don't know how to do it.
2 Answers
- Anonymous1 decade agoFavorite Answer
A simple formula for work problems like this is (A*B)/(A+B)=T.
A and B stand for the time of the two individual workers, while T represents the time it takes for them to complete the job TOGETHER.
A=6
B=?
C=4.5 or (9/2)
Plug these numbers into the problem:
(6*B)/(6+B)=(9/2)
Set it up like this:
6xB 9
------ = -----
6+B 2
Next, cross multiply by setting (6B)*(2)=(6+B)*(9)
Now, you have 12B=54+9B.
Subtract 9B from both sides to leave the variable on one side.
3B=54
Divide both sides by 3.
B=18
Your answer is 18, as given. This formula has many uses.
- 1 decade ago
3 hours because if theres two people you divide farmer As time by 2 and thats 3, 4.5-3=1.5.....then for farmer Bs time you multiply 1.5x2(because there were two people)and thats how you get your answer.
