Finding the Fourth Proportional to 1,399.65, 1,931.56 and 770.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.65 : 1,931.56 = 770.20 : x
2. Step 2: Convert to fraction form
   1,399.65/1,931.56 = 770.20/x
3. Step 3: Cross multiply
   1,399.65x = 1,931.56 × 770.20
4. Step 4: Simplify right side
   1,399.65x = 1,487,690.52
5. Step 5: Solve for x
   x = 1,487,690.52/1,399.65
6. Step 6: Final answer
   x = 1,062.90