**Solution:**

Let's assume there are x skilled workers and y unskilled workers.

**Average salary of unskilled workers:** ₹10,000

**Average salary of skilled workers:** ₹15,000

**Combined salary:** ₹12,000

We need to find the percentage of skilled workers.

**Step 1: Calculating the total salary of unskilled workers:**

Total salary of unskilled workers = Average salary of unskilled workers * Number of unskilled workers

Total salary of unskilled workers = ₹10,000 * y

**Step 2: Calculating the total salary of skilled workers:**

Total salary of skilled workers = Average salary of skilled workers * Number of skilled workers

Total salary of skilled workers = ₹15,000 * x

**Step 3: Forming the equation based on the given information:**

Total salary = Total salary of unskilled workers + Total salary of skilled workers

₹12,000 = ₹10,000 * y + ₹15,000 * x

**Step 4: Simplifying the equation:**

₹12,000 = ₹10,000y + ₹15,000x

Dividing the equation by ₹1,000, we get:

12 = 10y + 15x

**Step 5: Checking the options:**

Let's substitute the given options to check which one satisfies the equation.

a) 40% skilled workers:

If there are 40% skilled workers, then the remaining 60% would be unskilled workers.

x = 40% of total workers = 0.4 * (x + y)

y = 60% of total workers = 0.6 * (x + y)

Substituting these values in the equation:

12 = 10 * (0.6 * (x+y)) + 15 * (0.4 * (x+y))

Simplifying the equation, we get:

12 = 6(x + y) + 6(x + y)

12 = 12(x + y)

The equation is satisfied.

Therefore, the percentage of skilled workers is **40%**.

b) 50% skilled workers:

If there are 50% skilled workers, then the remaining 50% would be unskilled workers.

x = 50% of total workers = 0.5 * (x + y)

y = 50% of total workers = 0.5 * (x + y)

Substituting these values in the equation:

12 = 10 * (0.5 * (x+y)) + 15 * (0.5 * (x+y))

Simplifying the equation, we get:

12 = 5(x + y) + 7.5(x + y)

12 = 12.5(x + y)

The equation is not satisfied.

Therefore, the percentage of skilled workers is not 50%.

c) 60% skilled workers:

If there are 60% skilled workers, then the remaining 40% would be unskilled workers.

x = 60% of total workers = 0.6 * (x + y)

y = 40% of total workers = 0.4 * (x + y)

Substituting these values in the equation:

12 = 10 * (0.4 * (x+y)) + 15 *

Average salary of a group of unskilled workers is 10000, and the average salary of skilled workers is 15000 then here we have combined salary is 12000,by the formula combined average n1*10000+n2*15000/n1+n2=12000,therefore n1/n2 =2000/3000=