Finding the Fourth Proportional to 2,492.78, 3,739.25 and 643.89

Step by Step Solution

1. Step 1: Write the proportion equation
   2,492.78 : 3,739.25 = 643.89 : x
2. Step 2: Convert to fraction form
   2,492.78/3,739.25 = 643.89/x
3. Step 3: Cross multiply
   2,492.78x = 3,739.25 × 643.89
4. Step 4: Simplify right side
   2,492.78x = 2,407,662.46
5. Step 5: Solve for x
   x = 2,407,662.46/2,492.78
6. Step 6: Final answer
   x = 965.85