Finding the Third Proportional to 42.50 and 77

Step by Step Solution

1. Step 1: Write the proportion equation
   42.50 : 77 = 77 : x
2. Step 2: Convert to fraction form
   42.50/77 = 77/x
3. Step 3: Cross multiply
   42.50x = 77 × 77
4. Step 4: Simplify right side
   42.50x = 5,929
5. Step 5: Solve for x
   x = 5,929/42.50
6. Step 6: Final answer
   x = 139.51