Finding the Fourth Proportional to 2,591.34, 3,887.15 and 643.56

Step by Step Solution

1. Step 1: Write the proportion equation
   2,591.34 : 3,887.15 = 643.56 : x
2. Step 2: Convert to fraction form
   2,591.34/3,887.15 = 643.56/x
3. Step 3: Cross multiply
   2,591.34x = 3,887.15 × 643.56
4. Step 4: Simplify right side
   2,591.34x = 2,501,611.04
5. Step 5: Solve for x
   x = 2,501,611.04/2,591.34
6. Step 6: Final answer
   x = 965.37