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Finding the Fourth Proportional to 917.80, 1,376.70 and 431.40

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Solution

The fourth proportional to 917.80, 1,376.70 and 431.40 is: 647.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    917.80 : 1,376.70 = 431.40 : x
  2. Step 2: Convert to fraction form
    917.80/1,376.70 = 431.40/x
  3. Step 3: Cross multiply
    917.80x = 1,376.70 × 431.40
  4. Step 4: Simplify right side
    917.80x = 593,908.38
  5. Step 5: Solve for x
    x = 593,908.38/917.80
  6. Step 6: Final answer
    x = 647.10

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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.