Finding the Fourth Proportional to 1,109.16, 1,530.78 and 643.56

Step by Step Solution

1. Step 1: Write the proportion equation
   1,109.16 : 1,530.78 = 643.56 : x
2. Step 2: Convert to fraction form
   1,109.16/1,530.78 = 643.56/x
3. Step 3: Cross multiply
   1,109.16x = 1,530.78 × 643.56
4. Step 4: Simplify right side
   1,109.16x = 985,148.78
5. Step 5: Solve for x
   x = 985,148.78/1,109.16
6. Step 6: Final answer
   x = 888.19