Finding the Fourth Proportional to 1,111.16, 1,533.78 and 645.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,111.16 : 1,533.78 = 645.80 : x
2. Step 2: Convert to fraction form
   1,111.16/1,533.78 = 645.80/x
3. Step 3: Cross multiply
   1,111.16x = 1,533.78 × 645.80
4. Step 4: Simplify right side
   1,111.16x = 990,515.12
5. Step 5: Solve for x
   x = 990,515.12/1,111.16
6. Step 6: Final answer
   x = 891.42