Finding the Fourth Proportional to 387,978.05, 535,404.55 and 218,212.17

Step by Step Solution

1. Step 1: Write the proportion equation
   387,978.05 : 535,404.55 = 218,212.17 : x
2. Step 2: Convert to fraction form
   387,978.05/535,404.55 = 218,212.17/x
3. Step 3: Cross multiply
   387,978.05x = 535,404.55 × 218,212.17
4. Step 4: Simplify right side
   387,978.05x = 116,831,789,476.35
5. Step 5: Solve for x
   x = 116,831,789,476.35/387,978.05
6. Step 6: Final answer
   x = 301,129.90