Finding the Fourth Proportional to 1,105.74, 1,658.84 and 643.91

Step by Step Solution

1. Step 1: Write the proportion equation
   1,105.74 : 1,658.84 = 643.91 : x
2. Step 2: Convert to fraction form
   1,105.74/1,658.84 = 643.91/x
3. Step 3: Cross multiply
   1,105.74x = 1,658.84 × 643.91
4. Step 4: Simplify right side
   1,105.74x = 1,068,132.15
5. Step 5: Solve for x
   x = 1,068,132.15/1,105.74
6. Step 6: Final answer
   x = 965.99