Finding the Fourth Proportional to 1,387.06, 1,912.88 and 920.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,387.06 : 1,912.88 = 920.50 : x
2. Step 2: Convert to fraction form
   1,387.06/1,912.88 = 920.50/x
3. Step 3: Cross multiply
   1,387.06x = 1,912.88 × 920.50
4. Step 4: Simplify right side
   1,387.06x = 1,760,806.04
5. Step 5: Solve for x
   x = 1,760,806.04/1,387.06
6. Step 6: Final answer
   x = 1,269.45