Finding the Fourth Proportional to 1,866.57, 2,799.72 and 770.91

Step by Step Solution

1. Step 1: Write the proportion equation
   1,866.57 : 2,799.72 = 770.91 : x
2. Step 2: Convert to fraction form
   1,866.57/2,799.72 = 770.91/x
3. Step 3: Cross multiply
   1,866.57x = 2,799.72 × 770.91
4. Step 4: Simplify right side
   1,866.57x = 2,158,332.15
5. Step 5: Solve for x
   x = 2,158,332.15/1,866.57
6. Step 6: Final answer
   x = 1,156.31