Finding the Fourth Proportional to 2,591.56, 3,887.33 and 643.77

Step by Step Solution

1. Step 1: Write the proportion equation
   2,591.56 : 3,887.33 = 643.77 : x
2. Step 2: Convert to fraction form
   2,591.56/3,887.33 = 643.77/x
3. Step 3: Cross multiply
   2,591.56x = 3,887.33 × 643.77
4. Step 4: Simplify right side
   2,591.56x = 2,502,538.33
5. Step 5: Solve for x
   x = 2,502,538.33/2,591.56
6. Step 6: Final answer
   x = 965.65