Finding the Fourth Proportional to 1,055.34, 1,583.55 and 639.86

Step by Step Solution

1. Step 1: Write the proportion equation
   1,055.34 : 1,583.55 = 639.86 : x
2. Step 2: Convert to fraction form
   1,055.34/1,583.55 = 639.86/x
3. Step 3: Cross multiply
   1,055.34x = 1,583.55 × 639.86
4. Step 4: Simplify right side
   1,055.34x = 1,013,250.30
5. Step 5: Solve for x
   x = 1,013,250.30/1,055.34
6. Step 6: Final answer
   x = 960.12