Finding the Fourth Proportional to 1,080.72, 1,491.60 and 688.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,080.72 : 1,491.60 = 688.20 : x
2. Step 2: Convert to fraction form
   1,080.72/1,491.60 = 688.20/x
3. Step 3: Cross multiply
   1,080.72x = 1,491.60 × 688.20
4. Step 4: Simplify right side
   1,080.72x = 1,026,519.12
5. Step 5: Solve for x
   x = 1,026,519.12/1,080.72
6. Step 6: Final answer
   x = 949.85