Finding the Fourth Proportional to 1,098.50, 1,647.78 and 276.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,098.50 : 1,647.78 = 276.80 : x
2. Step 2: Convert to fraction form
   1,098.50/1,647.78 = 276.80/x
3. Step 3: Cross multiply
   1,098.50x = 1,647.78 × 276.80
4. Step 4: Simplify right side
   1,098.50x = 456,105.50
5. Step 5: Solve for x
   x = 456,105.50/1,098.50
6. Step 6: Final answer
   x = 415.21