Finding the Fourth Proportional to 1,985.31, 2,978.51 and 686.61

Step by Step Solution

1. Step 1: Write the proportion equation
   1,985.31 : 2,978.51 = 686.61 : x
2. Step 2: Convert to fraction form
   1,985.31/2,978.51 = 686.61/x
3. Step 3: Cross multiply
   1,985.31x = 2,978.51 × 686.61
4. Step 4: Simplify right side
   1,985.31x = 2,045,071.32
5. Step 5: Solve for x
   x = 2,045,071.32/1,985.31
6. Step 6: Final answer
   x = 1,030.10