Finding the Fourth Proportional to 1,399.63, 1,931.49 and 770.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.63 : 1,931.49 = 770.20 : x
2. Step 2: Convert to fraction form
   1,399.63/1,931.49 = 770.20/x
3. Step 3: Cross multiply
   1,399.63x = 1,931.49 × 770.20
4. Step 4: Simplify right side
   1,399.63x = 1,487,628.77
5. Step 5: Solve for x
   x = 1,487,628.77/1,399.63
6. Step 6: Final answer
   x = 1,062.87