Finding the Fourth Proportional to 1,005.48, 1,387.80 and 612.81

Step by Step Solution

1. Step 1: Write the proportion equation
   1,005.48 : 1,387.80 = 612.81 : x
2. Step 2: Convert to fraction form
   1,005.48/1,387.80 = 612.81/x
3. Step 3: Cross multiply
   1,005.48x = 1,387.80 × 612.81
4. Step 4: Simplify right side
   1,005.48x = 850,457.72
5. Step 5: Solve for x
   x = 850,457.72/1,005.48
6. Step 6: Final answer
   x = 845.82