Finding the Fourth Proportional to 1,380.78, 2,071.49 and 456.30

Step by Step Solution

1. Step 1: Write the proportion equation
   1,380.78 : 2,071.49 = 456.30 : x
2. Step 2: Convert to fraction form
   1,380.78/2,071.49 = 456.30/x
3. Step 3: Cross multiply
   1,380.78x = 2,071.49 × 456.30
4. Step 4: Simplify right side
   1,380.78x = 945,218.61
5. Step 5: Solve for x
   x = 945,218.61/1,380.78
6. Step 6: Final answer
   x = 684.55