Finding the Fourth Proportional to 1,216.88, 1,680.84 and 931.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,216.88 : 1,680.84 = 931.55 : x
2. Step 2: Convert to fraction form
   1,216.88/1,680.84 = 931.55/x
3. Step 3: Cross multiply
   1,216.88x = 1,680.84 × 931.55
4. Step 4: Simplify right side
   1,216.88x = 1,565,786.50
5. Step 5: Solve for x
   x = 1,565,786.50/1,216.88
6. Step 6: Final answer
   x = 1,286.72