Finding the Fourth Proportional to 1,399.78, 1,931.72 and 770.36

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.78 : 1,931.72 = 770.36 : x
2. Step 2: Convert to fraction form
   1,399.78/1,931.72 = 770.36/x
3. Step 3: Cross multiply
   1,399.78x = 1,931.72 × 770.36
4. Step 4: Simplify right side
   1,399.78x = 1,488,119.82
5. Step 5: Solve for x
   x = 1,488,119.82/1,399.78
6. Step 6: Final answer
   x = 1,063.11