Finding the Fourth Proportional to 2,139.10, 2,987.45 and 2,139.10

Step by Step Solution

1. Step 1: Write the proportion equation
   2,139.10 : 2,987.45 = 2,139.10 : x
2. Step 2: Convert to fraction form
   2,139.10/2,987.45 = 2,139.10/x
3. Step 3: Cross multiply
   2,139.10x = 2,987.45 × 2,139.10
4. Step 4: Simplify right side
   2,139.10x = 6,390,454.30
5. Step 5: Solve for x
   x = 6,390,454.30/2,139.10
6. Step 6: Final answer
   x = 2,987.45