Finding the Fourth Proportional to 1,005.89, 1,388.43 and 612.90

Step by Step Solution

1. Step 1: Write the proportion equation
   1,005.89 : 1,388.43 = 612.90 : x
2. Step 2: Convert to fraction form
   1,005.89/1,388.43 = 612.90/x
3. Step 3: Cross multiply
   1,005.89x = 1,388.43 × 612.90
4. Step 4: Simplify right side
   1,005.89x = 850,968.75
5. Step 5: Solve for x
   x = 850,968.75/1,005.89
6. Step 6: Final answer
   x = 845.99