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Finding the Fourth Proportional to 987.28, 1,362.64 and 638.40

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Solution

The fourth proportional to 987.28, 1,362.64 and 638.40 is: 881.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    987.28 : 1,362.64 = 638.40 : x
  2. Step 2: Convert to fraction form
    987.28/1,362.64 = 638.40/x
  3. Step 3: Cross multiply
    987.28x = 1,362.64 × 638.40
  4. Step 4: Simplify right side
    987.28x = 869,909.38
  5. Step 5: Solve for x
    x = 869,909.38/987.28
  6. Step 6: Final answer
    x = 881.12

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1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.