Finding the Fourth Proportional to 20,978.16, 31,478.21 and 8,499.51

Step by Step Solution

1. Step 1: Write the proportion equation
   20,978.16 : 31,478.21 = 8,499.51 : x
2. Step 2: Convert to fraction form
   20,978.16/31,478.21 = 8,499.51/x
3. Step 3: Cross multiply
   20,978.16x = 31,478.21 × 8,499.51
4. Step 4: Simplify right side
   20,978.16x = 267,549,360.68
5. Step 5: Solve for x
   x = 267,549,360.68/20,978.16
6. Step 6: Final answer
   x = 12,753.71