Finding the Fourth Proportional to 931.20, 1,398.72 and 758.16

Step by Step Solution

1. Step 1: Write the proportion equation
   931.20 : 1,398.72 = 758.16 : x
2. Step 2: Convert to fraction form
   931.20/1,398.72 = 758.16/x
3. Step 3: Cross multiply
   931.20x = 1,398.72 × 758.16
4. Step 4: Simplify right side
   931.20x = 1,060,453.56
5. Step 5: Solve for x
   x = 1,060,453.56/931.20
6. Step 6: Final answer
   x = 1,138.80