Some men and women are deployed to build a wall while the women destro...
The CAT category:
Problem:
The problem states that some men and women are deployed to build a wall while the women destroy it. The main construct the wall at the same rate, and the women destroy it at the same rate. The wall is built in 30 days when four men and five women are deployed. The same is completed in 20 days if five men and four women work on it. We need to find out how many days it will take for the wall to be built if 18 men and 18 women are engaged to work on it.
Solution:
To solve this problem, we will use the concept of man-days. The number of man-days required to complete a task is given by the product of the number of men and the number of days. Similarly, the number of woman-days required is given by the product of the number of women and the number of days.
Step 1: Calculate the man-days:
Let's calculate the man-days required to build the wall when four men and five women are deployed. We are given that the wall is built in 30 days. Using the concept of man-days, we can write the equation as:
4 * 30 = 120 man-days
Step 2: Calculate the woman-days:
Similarly, let's calculate the woman-days required to build the wall when four men and five women are deployed. Using the concept of woman-days, we can write the equation as:
5 * 30 = 150 woman-days
Step 3: Calculate the efficiency of men and women:
Now, let's calculate the efficiency of men and women. We know that the main constructs the wall at the same rate, so the efficiency of a man is equal to the efficiency of a woman.
Let the efficiency of a man be m and the efficiency of a woman be w. We can write the equations as:
4m + 5w = 1/30 (equation 1)
5m + 4w = 1/20 (equation 2)
Step 4: Solve the equations:
To solve the equations, we can use the method of substitution or elimination. Let's use the method of substitution:
From equation 1, we can express m in terms of w:
m = (1/30 - 5w)/4
Substituting this value of m in equation 2, we get:
5((1/30 - 5w)/4) + 4w = 1/20
Simplifying the equation, we get:
(1/24 - 25w/4) + 4w = 1/20
Solving for w, we get:
w = 1/600
Substituting the value of w in equation 1, we get:
m = 1/1200
Step 5: Calculate the number of days:
Now, let's calculate the number of days required to build the wall when 18 men and 18 women are deployed. We need to find the value of d in the equation:
18(1/1200) + 18(1/600) = 1/d
Simplifying the equation, we get:
1/66 + 3/100 = 1/d
Combining the fractions, we get
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