Finding the Fourth Proportional to 12,978.40, 19,461.20 and 4,212.18

Step by Step Solution

1. Step 1: Write the proportion equation
   12,978.40 : 19,461.20 = 4,212.18 : x
2. Step 2: Convert to fraction form
   12,978.40/19,461.20 = 4,212.18/x
3. Step 3: Cross multiply
   12,978.40x = 19,461.20 × 4,212.18
4. Step 4: Simplify right side
   12,978.40x = 81,974,077.42
5. Step 5: Solve for x
   x = 81,974,077.42/12,978.40
6. Step 6: Final answer
   x = 6,316.19