Finding the Fourth Proportional to 78.98, 108.72 and 71.21

Step by Step Solution

1. Step 1: Write the proportion equation
   78.98 : 108.72 = 71.21 : x
2. Step 2: Convert to fraction form
   78.98/108.72 = 71.21/x
3. Step 3: Cross multiply
   78.98x = 108.72 × 71.21
4. Step 4: Simplify right side
   78.98x = 7,741.95
5. Step 5: Solve for x
   x = 7,741.95/78.98
6. Step 6: Final answer
   x = 98.02