I need formula......................?

Question

asume the question i asked in http://answers.yahoo.com/question/index;_ylt=Ao3laV7GIjkPtqM8lMify1rsy6IX?qid=20060721064648AAYmy6s
was rephrased as follows how would you solve it? i need aformula. I need to understand how to solve these kind of problems.
(a) 2 boys can dig 5 wells in 3 days. how many boys can dig 5 wells in 2 days.
(b) 2 boys can dig 5wells in 3 days. how many days can 3 boys dig 5 wells
(c) 3 boys can dig 5 wells in 2 days. how many days can 2 boys dig 5 wells.

Answer 1

Use unity method to solve this

First find out the relationship b/w quantities: boys and days are inversely proportional; means more boys can do same work in less days and less boys can do same work in more days.....

Now make the different quantity 1, ie in (a) 3 days - 2 boys, 1 day 6 boys, 6 boys can finish the same work in 1 day, you divided days by 3 so multiply boys by 3.

Now as required days are 2 ie 2 * 1, so divide boys by 2 and the answer is 3 boys

Answer 2

I don't think that memorizing a formula will help you solve the problem. But...

If X boys dig Y wells in Z days, then the digging occurs at a rate R; R=Y/(XZ) wells/(boy·day). Then the number of wells W dug by B boys in D days is given by W=RBD, and rearranging gives D=W/(RB).

Answer 3

Say No of Boys=a, No of wells=b & No of days=c.
Then c=3*2/5(b/a)
(a) a=3*2/5(b/c)=1.2*5/2=3
(b) c=3*2/5(b/a)=1.2*5/3=2
(c) c=3*2/5(b/a)=1.2*5/2=3

Answer 4

(a) 3 boys: note that you can change number of days with number of boys without changing a result
(b) 2 days
(c) 3 days

Answer 5

it is a word problem there is no specific formulla 4 this as far as i know

Answer 6

study unitary method thoroughly.

Answer 7

(a) 4boys
(b) 2days
(c) 3 days