Finding the Third Proportional to 217,128 and 478,428

Step by Step Solution

1. Step 1: Write the proportion equation
   217,128 : 478,428 = 478,428 : x
2. Step 2: Convert to fraction form
   217,128/478,428 = 478,428/x
3. Step 3: Cross multiply
   217,128x = 478,428 × 478,428
4. Step 4: Simplify right side
   217,128x = 228,893,351,184
5. Step 5: Solve for x
   x = 228,893,351,184/217,128
6. Step 6: Final answer
   x = 1,054,186.25