Finding the Fourth Proportional to 1,128.20, 1,556.76 and 630.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,128.20 : 1,556.76 = 630.78 : x
2. Step 2: Convert to fraction form
   1,128.20/1,556.76 = 630.78/x
3. Step 3: Cross multiply
   1,128.20x = 1,556.76 × 630.78
4. Step 4: Simplify right side
   1,128.20x = 981,973.07
5. Step 5: Solve for x
   x = 981,973.07/1,128.20
6. Step 6: Final answer
   x = 870.39