Finding the Fourth Proportional to 1,398.35, 1,929.04 and 978.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,398.35 : 1,929.04 = 978.55 : x
2. Step 2: Convert to fraction form
   1,398.35/1,929.04 = 978.55/x
3. Step 3: Cross multiply
   1,398.35x = 1,929.04 × 978.55
4. Step 4: Simplify right side
   1,398.35x = 1,887,654.82
5. Step 5: Solve for x
   x = 1,887,654.82/1,398.35
6. Step 6: Final answer
   x = 1,349.91