Finding the Fourth Proportional to 1,225.15, 1,690.72 and 665.62

Step by Step Solution

1. Step 1: Write the proportion equation
   1,225.15 : 1,690.72 = 665.62 : x
2. Step 2: Convert to fraction form
   1,225.15/1,690.72 = 665.62/x
3. Step 3: Cross multiply
   1,225.15x = 1,690.72 × 665.62
4. Step 4: Simplify right side
   1,225.15x = 1,125,368.59
5. Step 5: Solve for x
   x = 1,125,368.59/1,225.15
6. Step 6: Final answer
   x = 918.56