Finding the Fourth Proportional to 78.72, 108.61 and 51.10

Step by Step Solution

1. Step 1: Write the proportion equation
   78.72 : 108.61 = 51.10 : x
2. Step 2: Convert to fraction form
   78.72/108.61 = 51.10/x
3. Step 3: Cross multiply
   78.72x = 108.61 × 51.10
4. Step 4: Simplify right side
   78.72x = 5,549.97
5. Step 5: Solve for x
   x = 5,549.97/78.72
6. Step 6: Final answer
   x = 70.50