Finding the Fourth Proportional to 78.96, 118.50 and 42.90

Step by Step Solution

1. Step 1: Write the proportion equation
   78.96 : 118.50 = 42.90 : x
2. Step 2: Convert to fraction form
   78.96/118.50 = 42.90/x
3. Step 3: Cross multiply
   78.96x = 118.50 × 42.90
4. Step 4: Simplify right side
   78.96x = 5,083.65
5. Step 5: Solve for x
   x = 5,083.65/78.96
6. Step 6: Final answer
   x = 64.38