Finding the Fourth Proportional to 15.78, 21.83 and 13.05

Step by Step Solution

1. Step 1: Write the proportion equation
   15.78 : 21.83 = 13.05 : x
2. Step 2: Convert to fraction form
   15.78/21.83 = 13.05/x
3. Step 3: Cross multiply
   15.78x = 21.83 × 13.05
4. Step 4: Simplify right side
   15.78x = 284.82
5. Step 5: Solve for x
   x = 284.82/15.78
6. Step 6: Final answer
   x = 18.05