Finding the Fourth Proportional to 78.45, 117.31 and 67.18

Step by Step Solution

1. Step 1: Write the proportion equation
   78.45 : 117.31 = 67.18 : x
2. Step 2: Convert to fraction form
   78.45/117.31 = 67.18/x
3. Step 3: Cross multiply
   78.45x = 117.31 × 67.18
4. Step 4: Simplify right side
   78.45x = 7,880.89
5. Step 5: Solve for x
   x = 7,880.89/78.45
6. Step 6: Final answer
   x = 100.46