Finding the Fourth Proportional to 1,012.30, 1,396.37 and 638.62

Step by Step Solution

1. Step 1: Write the proportion equation
   1,012.30 : 1,396.37 = 638.62 : x
2. Step 2: Convert to fraction form
   1,012.30/1,396.37 = 638.62/x
3. Step 3: Cross multiply
   1,012.30x = 1,396.37 × 638.62
4. Step 4: Simplify right side
   1,012.30x = 891,749.81
5. Step 5: Solve for x
   x = 891,749.81/1,012.30
6. Step 6: Final answer
   x = 880.91