Finding the Fourth Proportional to 1,387.61, 1,912.61 and 983.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,387.61 : 1,912.61 = 983.31 : x
2. Step 2: Convert to fraction form
   1,387.61/1,912.61 = 983.31/x
3. Step 3: Cross multiply
   1,387.61x = 1,912.61 × 983.31
4. Step 4: Simplify right side
   1,387.61x = 1,880,683.62
5. Step 5: Solve for x
   x = 1,880,683.62/1,387.61
6. Step 6: Final answer
   x = 1,355.35