Finding the Fourth Proportional to 1,191.70, 1,783.90 and 642.52

Step by Step Solution

1. Step 1: Write the proportion equation
   1,191.70 : 1,783.90 = 642.52 : x
2. Step 2: Convert to fraction form
   1,191.70/1,783.90 = 642.52/x
3. Step 3: Cross multiply
   1,191.70x = 1,783.90 × 642.52
4. Step 4: Simplify right side
   1,191.70x = 1,146,191.43
5. Step 5: Solve for x
   x = 1,146,191.43/1,191.70
6. Step 6: Final answer
   x = 961.81