Finding the Fourth Proportional to 89.69, 123.70 and 78.75

Step by Step Solution

1. Step 1: Write the proportion equation
   89.69 : 123.70 = 78.75 : x
2. Step 2: Convert to fraction form
   89.69/123.70 = 78.75/x
3. Step 3: Cross multiply
   89.69x = 123.70 × 78.75
4. Step 4: Simplify right side
   89.69x = 9,741.38
5. Step 5: Solve for x
   x = 9,741.38/89.69
6. Step 6: Final answer
   x = 108.61