Finding the Fourth Proportional to 1,140.72, 1,574.04 and 643.28

Step by Step Solution

1. Step 1: Write the proportion equation
   1,140.72 : 1,574.04 = 643.28 : x
2. Step 2: Convert to fraction form
   1,140.72/1,574.04 = 643.28/x
3. Step 3: Cross multiply
   1,140.72x = 1,574.04 × 643.28
4. Step 4: Simplify right side
   1,140.72x = 1,012,548.45
5. Step 5: Solve for x
   x = 1,012,548.45/1,140.72
6. Step 6: Final answer
   x = 887.64