Finding the Fourth Proportional to 1,215.20, 1,676.88 and 691.12

Step by Step Solution

1. Step 1: Write the proportion equation
   1,215.20 : 1,676.88 = 691.12 : x
2. Step 2: Convert to fraction form
   1,215.20/1,676.88 = 691.12/x
3. Step 3: Cross multiply
   1,215.20x = 1,676.88 × 691.12
4. Step 4: Simplify right side
   1,215.20x = 1,158,925.31
5. Step 5: Solve for x
   x = 1,158,925.31/1,215.20
6. Step 6: Final answer
   x = 953.69