Finding the Fourth Proportional to 1,080.93, 1,491.72 and 639.21

Step by Step Solution

1. Step 1: Write the proportion equation
   1,080.93 : 1,491.72 = 639.21 : x
2. Step 2: Convert to fraction form
   1,080.93/1,491.72 = 639.21/x
3. Step 3: Cross multiply
   1,080.93x = 1,491.72 × 639.21
4. Step 4: Simplify right side
   1,080.93x = 953,522.34
5. Step 5: Solve for x
   x = 953,522.34/1,080.93
6. Step 6: Final answer
   x = 882.13