Finding the Fourth Proportional to 1,389.42, 2,082.31 and 772.81

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.42 : 2,082.31 = 772.81 : x
2. Step 2: Convert to fraction form
   1,389.42/2,082.31 = 772.81/x
3. Step 3: Cross multiply
   1,389.42x = 2,082.31 × 772.81
4. Step 4: Simplify right side
   1,389.42x = 1,609,222.85
5. Step 5: Solve for x
   x = 1,609,222.85/1,389.42
6. Step 6: Final answer
   x = 1,158.20