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Finding the Fourth Proportional to 1,187.39, 1,638.35 and 689.78

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Solution

The fourth proportional to 1,187.39, 1,638.35 and 689.78 is: 951.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,187.39 : 1,638.35 = 689.78 : x
  2. Step 2: Convert to fraction form
    1,187.39/1,638.35 = 689.78/x
  3. Step 3: Cross multiply
    1,187.39x = 1,638.35 × 689.78
  4. Step 4: Simplify right side
    1,187.39x = 1,130,092.87
  5. Step 5: Solve for x
    x = 1,130,092.87/1,187.39
  6. Step 6: Final answer
    x = 951.75

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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.