Finding the Fourth Proportional to 1,136.63, 1,568.56 and 639.28

Step by Step Solution

1. Step 1: Write the proportion equation
   1,136.63 : 1,568.56 = 639.28 : x
2. Step 2: Convert to fraction form
   1,136.63/1,568.56 = 639.28/x
3. Step 3: Cross multiply
   1,136.63x = 1,568.56 × 639.28
4. Step 4: Simplify right side
   1,136.63x = 1,002,743.52
5. Step 5: Solve for x
   x = 1,002,743.52/1,136.63
6. Step 6: Final answer
   x = 882.21