Finding the Fourth Proportional to 1,355.20, 1,870.16 and 765.76

Step by Step Solution

1. Step 1: Write the proportion equation
   1,355.20 : 1,870.16 = 765.76 : x
2. Step 2: Convert to fraction form
   1,355.20/1,870.16 = 765.76/x
3. Step 3: Cross multiply
   1,355.20x = 1,870.16 × 765.76
4. Step 4: Simplify right side
   1,355.20x = 1,432,093.72
5. Step 5: Solve for x
   x = 1,432,093.72/1,355.20
6. Step 6: Final answer
   x = 1,056.74