Finding the Fourth Proportional to 1,288.89, 1,931.72 and 638.19

Step by Step Solution

1. Step 1: Write the proportion equation
   1,288.89 : 1,931.72 = 638.19 : x
2. Step 2: Convert to fraction form
   1,288.89/1,931.72 = 638.19/x
3. Step 3: Cross multiply
   1,288.89x = 1,931.72 × 638.19
4. Step 4: Simplify right side
   1,288.89x = 1,232,801.20
5. Step 5: Solve for x
   x = 1,232,801.20/1,288.89
6. Step 6: Final answer
   x = 956.48