Finding the Fourth Proportional to 1,398.54, 1,929.91 and 777.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,398.54 : 1,929.91 = 777.50 : x
2. Step 2: Convert to fraction form
   1,398.54/1,929.91 = 777.50/x
3. Step 3: Cross multiply
   1,398.54x = 1,929.91 × 777.50
4. Step 4: Simplify right side
   1,398.54x = 1,500,505.03
5. Step 5: Solve for x
   x = 1,500,505.03/1,398.54
6. Step 6: Final answer
   x = 1,072.91