Finding the Fourth Proportional to 42,807.88, 64,200.78 and 12,816.20

Step by Step Solution

1. Step 1: Write the proportion equation
   42,807.88 : 64,200.78 = 12,816.20 : x
2. Step 2: Convert to fraction form
   42,807.88/64,200.78 = 12,816.20/x
3. Step 3: Cross multiply
   42,807.88x = 64,200.78 × 12,816.20
4. Step 4: Simplify right side
   42,807.88x = 822,810,036.64
5. Step 5: Solve for x
   x = 822,810,036.64/42,807.88
6. Step 6: Final answer
   x = 19,220.99