Finding the Fourth Proportional to 1,111.28, 1,533.60 and 645.56

Step by Step Solution

1. Step 1: Write the proportion equation
   1,111.28 : 1,533.60 = 645.56 : x
2. Step 2: Convert to fraction form
   1,111.28/1,533.60 = 645.56/x
3. Step 3: Cross multiply
   1,111.28x = 1,533.60 × 645.56
4. Step 4: Simplify right side
   1,111.28x = 990,030.82
5. Step 5: Solve for x
   x = 990,030.82/1,111.28
6. Step 6: Final answer
   x = 890.89