Finding the Fourth Proportional to 1,055.38, 1,582.98 and 643.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,055.38 : 1,582.98 = 643.72 : x
2. Step 2: Convert to fraction form
   1,055.38/1,582.98 = 643.72/x
3. Step 3: Cross multiply
   1,055.38x = 1,582.98 × 643.72
4. Step 4: Simplify right side
   1,055.38x = 1,018,995.89
5. Step 5: Solve for x
   x = 1,018,995.89/1,055.38
6. Step 6: Final answer
   x = 965.53