Finding the Fourth Proportional to 78.70, 117.96 and 42.70

Step by Step Solution

1. Step 1: Write the proportion equation
   78.70 : 117.96 = 42.70 : x
2. Step 2: Convert to fraction form
   78.70/117.96 = 42.70/x
3. Step 3: Cross multiply
   78.70x = 117.96 × 42.70
4. Step 4: Simplify right side
   78.70x = 5,036.89
5. Step 5: Solve for x
   x = 5,036.89/78.70
6. Step 6: Final answer
   x = 64.00