Finding the Fourth Proportional to 1,216.72, 1,679.88 and 823.60

Step by Step Solution

1. Step 1: Write the proportion equation
   1,216.72 : 1,679.88 = 823.60 : x
2. Step 2: Convert to fraction form
   1,216.72/1,679.88 = 823.60/x
3. Step 3: Cross multiply
   1,216.72x = 1,679.88 × 823.60
4. Step 4: Simplify right side
   1,216.72x = 1,383,549.17
5. Step 5: Solve for x
   x = 1,383,549.17/1,216.72
6. Step 6: Final answer
   x = 1,137.11