Question

(1) If 10 men can make 12 tables in 6 days, how long would 6 men take to make 36 tables?
(2) A family of 6 ate 240kg bag of rice in 10 days, in how many days will a family of 3 eat a 120kg bag of rice?
(3) If 12 boys row a boat across a river 8km long in 5 hours, how long will it take 18 boys to row across a river 10km long?

Answer 1

I think for number one, it is 18.

Answer 2

I will do the first, you do the others in the same way

method 1:
10 men can make 12 tables in 6 days
30 men can make 36 tables in 6 days
6 men can make 12 tables <b>in 30 days</b> <------ I divided "men" by 5, then had to multiply "days" by 5

(common sense in the above: if you decrease the number of men on a job, it will take longer.
So if you divide "men" by some number, you must multiply "days" by the same number to get the
same number of tables )

Method 2
number of chairs = a*man-days
given:
12 = a(10)(6)
a = 12/60 = 1/5(6)(men)


number of chairs = (1/5)(man-days)
36 = (1/5)(6)(men)
men = 36*5/6 = 30, same as above

How did you get 18?