Finding the Fourth Proportional to 1,140.79, 1,574.27 and 643.42

Step by Step Solution

1. Step 1: Write the proportion equation
   1,140.79 : 1,574.27 = 643.42 : x
2. Step 2: Convert to fraction form
   1,140.79/1,574.27 = 643.42/x
3. Step 3: Cross multiply
   1,140.79x = 1,574.27 × 643.42
4. Step 4: Simplify right side
   1,140.79x = 1,012,905.71
5. Step 5: Solve for x
   x = 1,012,905.71/1,140.79
6. Step 6: Final answer
   x = 887.90