Finding the Fourth Proportional to 1,428.21, 1,970.96 and 1,009.30

Step by Step Solution

1. Step 1: Write the proportion equation
   1,428.21 : 1,970.96 = 1,009.30 : x
2. Step 2: Convert to fraction form
   1,428.21/1,970.96 = 1,009.30/x
3. Step 3: Cross multiply
   1,428.21x = 1,970.96 × 1,009.30
4. Step 4: Simplify right side
   1,428.21x = 1,989,283.72
5. Step 5: Solve for x
   x = 1,989,283.72/1,428.21
6. Step 6: Final answer
   x = 1,392.85