Finding the Fourth Proportional to 1,399.91, 1,931.98 and 770.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.91 : 1,931.98 = 770.55 : x
2. Step 2: Convert to fraction form
   1,399.91/1,931.98 = 770.55/x
3. Step 3: Cross multiply
   1,399.91x = 1,931.98 × 770.55
4. Step 4: Simplify right side
   1,399.91x = 1,488,688.15
5. Step 5: Solve for x
   x = 1,488,688.15/1,399.91
6. Step 6: Final answer
   x = 1,063.42