Finding the Fourth Proportional to 12,978.10, 17,909.40 and 7,312.74

Step by Step Solution

1. Step 1: Write the proportion equation
   12,978.10 : 17,909.40 = 7,312.74 : x
2. Step 2: Convert to fraction form
   12,978.10/17,909.40 = 7,312.74/x
3. Step 3: Cross multiply
   12,978.10x = 17,909.40 × 7,312.74
4. Step 4: Simplify right side
   12,978.10x = 130,966,871.94
5. Step 5: Solve for x
   x = 130,966,871.94/12,978.10
6. Step 6: Final answer
   x = 10,091.38