Finding the Fourth Proportional to 1,017.42, 1,403.16 and 643.98

Step by Step Solution

1. Step 1: Write the proportion equation
   1,017.42 : 1,403.16 = 643.98 : x
2. Step 2: Convert to fraction form
   1,017.42/1,403.16 = 643.98/x
3. Step 3: Cross multiply
   1,017.42x = 1,403.16 × 643.98
4. Step 4: Simplify right side
   1,017.42x = 903,606.98
5. Step 5: Solve for x
   x = 903,606.98/1,017.42
6. Step 6: Final answer
   x = 888.14