Finding the Fourth Proportional to 1,055.02, 1,580.70 and 642.88

Step by Step Solution

1. Step 1: Write the proportion equation
   1,055.02 : 1,580.70 = 642.88 : x
2. Step 2: Convert to fraction form
   1,055.02/1,580.70 = 642.88/x
3. Step 3: Cross multiply
   1,055.02x = 1,580.70 × 642.88
4. Step 4: Simplify right side
   1,055.02x = 1,016,200.42
5. Step 5: Solve for x
   x = 1,016,200.42/1,055.02
6. Step 6: Final answer
   x = 963.20