Finding the Fourth Proportional to 1,293.72, 1,939.86 and 643.56

Step by Step Solution

1. Step 1: Write the proportion equation
   1,293.72 : 1,939.86 = 643.56 : x
2. Step 2: Convert to fraction form
   1,293.72/1,939.86 = 643.56/x
3. Step 3: Cross multiply
   1,293.72x = 1,939.86 × 643.56
4. Step 4: Simplify right side
   1,293.72x = 1,248,416.30
5. Step 5: Solve for x
   x = 1,248,416.30/1,293.72
6. Step 6: Final answer
   x = 964.98