Finding the Fourth Proportional to 78.16, 117.34 and 45.72

Step by Step Solution

1. Step 1: Write the proportion equation
   78.16 : 117.34 = 45.72 : x
2. Step 2: Convert to fraction form
   78.16/117.34 = 45.72/x
3. Step 3: Cross multiply
   78.16x = 117.34 × 45.72
4. Step 4: Simplify right side
   78.16x = 5,364.78
5. Step 5: Solve for x
   x = 5,364.78/78.16
6. Step 6: Final answer
   x = 68.64