Finding the Fourth Proportional to 1,238.43, 1,709.05 and 678.89

Step by Step Solution

1. Step 1: Write the proportion equation
   1,238.43 : 1,709.05 = 678.89 : x
2. Step 2: Convert to fraction form
   1,238.43/1,709.05 = 678.89/x
3. Step 3: Cross multiply
   1,238.43x = 1,709.05 × 678.89
4. Step 4: Simplify right side
   1,238.43x = 1,160,256.95
5. Step 5: Solve for x
   x = 1,160,256.95/1,238.43
6. Step 6: Final answer
   x = 936.88