Finding the Fourth Proportional to 5,280.72, 7,920.90 and 1,385.10

Step by Step Solution

1. Step 1: Write the proportion equation
   5,280.72 : 7,920.90 = 1,385.10 : x
2. Step 2: Convert to fraction form
   5,280.72/7,920.90 = 1,385.10/x
3. Step 3: Cross multiply
   5,280.72x = 7,920.90 × 1,385.10
4. Step 4: Simplify right side
   5,280.72x = 10,971,238.59
5. Step 5: Solve for x
   x = 10,971,238.59/5,280.72
6. Step 6: Final answer
   x = 2,077.60