Finding the Fourth Proportional to 1,017.72, 1,405.08 and 645.24

Step by Step Solution

1. Step 1: Write the proportion equation
   1,017.72 : 1,405.08 = 645.24 : x
2. Step 2: Convert to fraction form
   1,017.72/1,405.08 = 645.24/x
3. Step 3: Cross multiply
   1,017.72x = 1,405.08 × 645.24
4. Step 4: Simplify right side
   1,017.72x = 906,613.82
5. Step 5: Solve for x
   x = 906,613.82/1,017.72
6. Step 6: Final answer
   x = 890.83