Finding the Fourth Proportional to 1,398.60, 1,929.37 and 978.79

Step by Step Solution

1. Step 1: Write the proportion equation
   1,398.60 : 1,929.37 = 978.79 : x
2. Step 2: Convert to fraction form
   1,398.60/1,929.37 = 978.79/x
3. Step 3: Cross multiply
   1,398.60x = 1,929.37 × 978.79
4. Step 4: Simplify right side
   1,398.60x = 1,888,448.06
5. Step 5: Solve for x
   x = 1,888,448.06/1,398.60
6. Step 6: Final answer
   x = 1,350.24