Finding the Third Proportional to 428 and 1,128.50

Step by Step Solution

1. Step 1: Write the proportion equation
   428 : 1,128.50 = 1,128.50 : x
2. Step 2: Convert to fraction form
   428/1,128.50 = 1,128.50/x
3. Step 3: Cross multiply
   428x = 1,128.50 × 1,128.50
4. Step 4: Simplify right side
   428x = 1,273,512.25
5. Step 5: Solve for x
   x = 1,273,512.25/428
6. Step 6: Final answer
   x = 2,975.50