Finding the Fourth Proportional to 1,016.62, 1,402.18 and 643.28

Step by Step Solution

1. Step 1: Write the proportion equation
   1,016.62 : 1,402.18 = 643.28 : x
2. Step 2: Convert to fraction form
   1,016.62/1,402.18 = 643.28/x
3. Step 3: Cross multiply
   1,016.62x = 1,402.18 × 643.28
4. Step 4: Simplify right side
   1,016.62x = 901,985.73
5. Step 5: Solve for x
   x = 901,985.73/1,016.62
6. Step 6: Final answer
   x = 887.24