Finding the Fourth Proportional to 978.78, 1,469.38 and 905.88

Step by Step Solution

1. Step 1: Write the proportion equation
   978.78 : 1,469.38 = 905.88 : x
2. Step 2: Convert to fraction form
   978.78/1,469.38 = 905.88/x
3. Step 3: Cross multiply
   978.78x = 1,469.38 × 905.88
4. Step 4: Simplify right side
   978.78x = 1,331,081.95
5. Step 5: Solve for x
   x = 1,331,081.95/978.78
6. Step 6: Final answer
   x = 1,359.94