Finding the Fourth Proportional to 1,013.92, 1,405.72 and 978.28

Step by Step Solution

1. Step 1: Write the proportion equation
   1,013.92 : 1,405.72 = 978.28 : x
2. Step 2: Convert to fraction form
   1,013.92/1,405.72 = 978.28/x
3. Step 3: Cross multiply
   1,013.92x = 1,405.72 × 978.28
4. Step 4: Simplify right side
   1,013.92x = 1,375,187.76
5. Step 5: Solve for x
   x = 1,375,187.76/1,013.92
6. Step 6: Final answer
   x = 1,356.31