Finding the Fourth Proportional to 143,728.21, 215,705.31 and 99,665.02

Step by Step Solution

1. Step 1: Write the proportion equation
   143,728.21 : 215,705.31 = 99,665.02 : x
2. Step 2: Convert to fraction form
   143,728.21/215,705.31 = 99,665.02/x
3. Step 3: Cross multiply
   143,728.21x = 215,705.31 × 99,665.02
4. Step 4: Simplify right side
   143,728.21x = 21,498,274,035.26
5. Step 5: Solve for x
   x = 21,498,274,035.26/143,728.21
6. Step 6: Final answer
   x = 149,575.88