Finding the Fourth Proportional to 12,686.79, 17,507.41 and 7,021.78

Step by Step Solution

1. Step 1: Write the proportion equation
   12,686.79 : 17,507.41 = 7,021.78 : x
2. Step 2: Convert to fraction form
   12,686.79/17,507.41 = 7,021.78/x
3. Step 3: Cross multiply
   12,686.79x = 17,507.41 × 7,021.78
4. Step 4: Simplify right side
   12,686.79x = 122,933,181.39
5. Step 5: Solve for x
   x = 122,933,181.39/12,686.79
6. Step 6: Final answer
   x = 9,689.86