Finding the Fourth Proportional to 1,139.56, 1,710.30 and 490.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.56 : 1,710.30 = 490.78 : x
2. Step 2: Convert to fraction form
   1,139.56/1,710.30 = 490.78/x
3. Step 3: Cross multiply
   1,139.56x = 1,710.30 × 490.78
4. Step 4: Simplify right side
   1,139.56x = 839,381.03
5. Step 5: Solve for x
   x = 839,381.03/1,139.56
6. Step 6: Final answer
   x = 736.58