Finding the Fourth Proportional to 1,038.69, 1,558.17 and 643.77

Step by Step Solution

1. Step 1: Write the proportion equation
   1,038.69 : 1,558.17 = 643.77 : x
2. Step 2: Convert to fraction form
   1,038.69/1,558.17 = 643.77/x
3. Step 3: Cross multiply
   1,038.69x = 1,558.17 × 643.77
4. Step 4: Simplify right side
   1,038.69x = 1,003,103.10
5. Step 5: Solve for x
   x = 1,003,103.10/1,038.69
6. Step 6: Final answer
   x = 965.74