Finding the Fourth Proportional to 1,089.29, 1,635.09 and 678.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,089.29 : 1,635.09 = 678.72 : x
2. Step 2: Convert to fraction form
   1,089.29/1,635.09 = 678.72/x
3. Step 3: Cross multiply
   1,089.29x = 1,635.09 × 678.72
4. Step 4: Simplify right side
   1,089.29x = 1,109,768.28
5. Step 5: Solve for x
   x = 1,109,768.28/1,089.29
6. Step 6: Final answer
   x = 1,018.80