Finding the Third Proportional to 300.19 and 643.69

Step by Step Solution

1. Step 1: Write the proportion equation
   300.19 : 643.69 = 643.69 : x
2. Step 2: Convert to fraction form
   300.19/643.69 = 643.69/x
3. Step 3: Cross multiply
   300.19x = 643.69 × 643.69
4. Step 4: Simplify right side
   300.19x = 414,333.60
5. Step 5: Solve for x
   x = 414,333.60/300.19
6. Step 6: Final answer
   x = 1,380.25