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Finding the Fourth Proportional to 860.40, 1,288.80 and 643.68

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Solution

The fourth proportional to 860.40, 1,288.80 and 643.68 is: 964.17

Step by Step Solution

  1. Step 1: Write the proportion equation
    860.40 : 1,288.80 = 643.68 : x
  2. Step 2: Convert to fraction form
    860.40/1,288.80 = 643.68/x
  3. Step 3: Cross multiply
    860.40x = 1,288.80 × 643.68
  4. Step 4: Simplify right side
    860.40x = 829,574.78
  5. Step 5: Solve for x
    x = 829,574.78/860.40
  6. Step 6: Final answer
    x = 964.17

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.