Finding the Fourth Proportional to 78.77, 108.72 and 51.21

Step by Step Solution

1. Step 1: Write the proportion equation
   78.77 : 108.72 = 51.21 : x
2. Step 2: Convert to fraction form
   78.77/108.72 = 51.21/x
3. Step 3: Cross multiply
   78.77x = 108.72 × 51.21
4. Step 4: Simplify right side
   78.77x = 5,567.55
5. Step 5: Solve for x
   x = 5,567.55/78.77
6. Step 6: Final answer
   x = 70.68