Finding the Fourth Proportional to 42.77, 64.17 and 18.72

Step by Step Solution

1. Step 1: Write the proportion equation
   42.77 : 64.17 = 18.72 : x
2. Step 2: Convert to fraction form
   42.77/64.17 = 18.72/x
3. Step 3: Cross multiply
   42.77x = 64.17 × 18.72
4. Step 4: Simplify right side
   42.77x = 1,201.26
5. Step 5: Solve for x
   x = 1,201.26/42.77
6. Step 6: Final answer
   x = 28.09