Finding the Fourth Proportional to 1,005.78, 1,387.98 and 607.68

Step by Step Solution

1. Step 1: Write the proportion equation
   1,005.78 : 1,387.98 = 607.68 : x
2. Step 2: Convert to fraction form
   1,005.78/1,387.98 = 607.68/x
3. Step 3: Cross multiply
   1,005.78x = 1,387.98 × 607.68
4. Step 4: Simplify right side
   1,005.78x = 843,447.69
5. Step 5: Solve for x
   x = 843,447.69/1,005.78
6. Step 6: Final answer
   x = 838.60