Finding the Fourth Proportional to 1,385.78, 1,912.29 and 764.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,385.78 : 1,912.29 = 764.78 : x
2. Step 2: Convert to fraction form
   1,385.78/1,912.29 = 764.78/x
3. Step 3: Cross multiply
   1,385.78x = 1,912.29 × 764.78
4. Step 4: Simplify right side
   1,385.78x = 1,462,481.15
5. Step 5: Solve for x
   x = 1,462,481.15/1,385.78
6. Step 6: Final answer
   x = 1,055.35