Finding the Fourth Proportional to 1,386.72, 1,913.66 and 765.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,386.72 : 1,913.66 = 765.72 : x
2. Step 2: Convert to fraction form
   1,386.72/1,913.66 = 765.72/x
3. Step 3: Cross multiply
   1,386.72x = 1,913.66 × 765.72
4. Step 4: Simplify right side
   1,386.72x = 1,465,326.78
5. Step 5: Solve for x
   x = 1,465,326.78/1,386.72
6. Step 6: Final answer
   x = 1,056.69