Finding the Third Proportional to 30.61 and 64.78

Step by Step Solution

1. Step 1: Write the proportion equation
   30.61 : 64.78 = 64.78 : x
2. Step 2: Convert to fraction form
   30.61/64.78 = 64.78/x
3. Step 3: Cross multiply
   30.61x = 64.78 × 64.78
4. Step 4: Simplify right side
   30.61x = 4,196.99
5. Step 5: Solve for x
   x = 4,196.99/30.61
6. Step 6: Final answer
   x = 137.10