Finding the Fourth Proportional to 12,991.63, 19,459.25 and 7,978.79

Step by Step Solution

1. Step 1: Write the proportion equation
   12,991.63 : 19,459.25 = 7,978.79 : x
2. Step 2: Convert to fraction form
   12,991.63/19,459.25 = 7,978.79/x
3. Step 3: Cross multiply
   12,991.63x = 19,459.25 × 7,978.79
4. Step 4: Simplify right side
   12,991.63x = 155,261,269.31
5. Step 5: Solve for x
   x = 155,261,269.31/12,991.63
6. Step 6: Final answer
   x = 11,950.87