Finding the Fourth Proportional to 42.78, 64.17 and 15.35

Step by Step Solution

1. Step 1: Write the proportion equation
   42.78 : 64.17 = 15.35 : x
2. Step 2: Convert to fraction form
   42.78/64.17 = 15.35/x
3. Step 3: Cross multiply
   42.78x = 64.17 × 15.35
4. Step 4: Simplify right side
   42.78x = 985.01
5. Step 5: Solve for x
   x = 985.01/42.78
6. Step 6: Final answer
   x = 23.03