Finding the Fourth Proportional to 1,398.21, 1,929.59 and 768.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,398.21 : 1,929.59 = 768.80 : x
2. Step 2: Convert to fraction form
   1,398.21/1,929.59 = 768.80/x
3. Step 3: Cross multiply
   1,398.21x = 1,929.59 × 768.80
4. Step 4: Simplify right side
   1,398.21x = 1,483,455.30
5. Step 5: Solve for x
   x = 1,483,455.30/1,398.21
6. Step 6: Final answer
   x = 1,060.97