Finding the Fourth Proportional to 1,386.80, 1,913.72 and 765.84

Step by Step Solution

1. Step 1: Write the proportion equation
   1,386.80 : 1,913.72 = 765.84 : x
2. Step 2: Convert to fraction form
   1,386.80/1,913.72 = 765.84/x
3. Step 3: Cross multiply
   1,386.80x = 1,913.72 × 765.84
4. Step 4: Simplify right side
   1,386.80x = 1,465,603.32
5. Step 5: Solve for x
   x = 1,465,603.32/1,386.80
6. Step 6: Final answer
   x = 1,056.82