Finding the Third Proportional to 428.34 and 641.53

Step by Step Solution

1. Step 1: Write the proportion equation
   428.34 : 641.53 = 641.53 : x
2. Step 2: Convert to fraction form
   428.34/641.53 = 641.53/x
3. Step 3: Cross multiply
   428.34x = 641.53 × 641.53
4. Step 4: Simplify right side
   428.34x = 411,562.34
5. Step 5: Solve for x
   x = 411,562.34/428.34
6. Step 6: Final answer
   x = 960.82