Finding the Fourth Proportional to 1,005.98, 1,388.55 and 613.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,005.98 : 1,388.55 = 613.20 : x
2. Step 2: Convert to fraction form
   1,005.98/1,388.55 = 613.20/x
3. Step 3: Cross multiply
   1,005.98x = 1,388.55 × 613.20
4. Step 4: Simplify right side
   1,005.98x = 851,458.86
5. Step 5: Solve for x
   x = 851,458.86/1,005.98
6. Step 6: Final answer
   x = 846.40