Finding the Fourth Proportional to 1,128.61, 1,691.34 and 510.81

Step by Step Solution

1. Step 1: Write the proportion equation
   1,128.61 : 1,691.34 = 510.81 : x
2. Step 2: Convert to fraction form
   1,128.61/1,691.34 = 510.81/x
3. Step 3: Cross multiply
   1,128.61x = 1,691.34 × 510.81
4. Step 4: Simplify right side
   1,128.61x = 863,953.39
5. Step 5: Solve for x
   x = 863,953.39/1,128.61
6. Step 6: Final answer
   x = 765.50