Finding the Fourth Proportional to 12,915.96, 19,369.74 and 7,978.20

Step by Step Solution

1. Step 1: Write the proportion equation
   12,915.96 : 19,369.74 = 7,978.20 : x
2. Step 2: Convert to fraction form
   12,915.96/19,369.74 = 7,978.20/x
3. Step 3: Cross multiply
   12,915.96x = 19,369.74 × 7,978.20
4. Step 4: Simplify right side
   12,915.96x = 154,535,659.67
5. Step 5: Solve for x
   x = 154,535,659.67/12,915.96
6. Step 6: Final answer
   x = 11,964.71