Finding the Fourth Proportional to 613,188, 919,905 and 213,721.50

Step by Step Solution

1. Step 1: Write the proportion equation
   613,188 : 919,905 = 213,721.50 : x
2. Step 2: Convert to fraction form
   613,188/919,905 = 213,721.50/x
3. Step 3: Cross multiply
   613,188x = 919,905 × 213,721.50
4. Step 4: Simplify right side
   613,188x = 196,603,476,457.50
5. Step 5: Solve for x
   x = 196,603,476,457.50/613,188
6. Step 6: Final answer
   x = 320,625.12