How to Solve Time and Work Problems #3 Fast Method

This time, our topic of discussion will be those problems in which a number of workers i.e. men and women or men and boys are given a task and we have to determine how much time they will take to perform the given task. The type of questions as you already know, are asked in many competitive exams and other exams.
Suppose we are given a problem like given below
Q: If 4 men or 6 boys can do a task in 12 days then 10 men and 3 boys will do that task in how many days?
Now carefully read the question. In the first line, 4 men or 6 boys are given but the question is asked with 10 men and 3 boys means men and boys combined.
If you do this question by its normal computational method, then it will take time of about 2-3 minutes to solve. But I am giving you a trick here to solve this type of question that will solve this question in seconds. You just have to put the formula and you will get the answer. Is not it so simple.
So we should learn the rule for this type of questions.
Rule:- if m1 men or b1 boys does a task in d1 days then m2 men and b2 boys will do it in
                                =(m1b1d1)/(m1b2+m2b1)           days
                So the solution to the above problem will be
                10 men and 3 boys will do the work in
                                =(4*6*12)/(4*3+10*6)  days
                                =24*12/(12+60)                days
                                =4 days
So 10 men and 3 boys will do the same task in just 4 days. This is the shortest trick you can find for this type of question.
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