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Finding the Fourth Proportional to 1,005.21, 1,387.09 and 690.75

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Solution

The fourth proportional to 1,005.21, 1,387.09 and 690.75 is: 953.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,005.21 : 1,387.09 = 690.75 : x
  2. Step 2: Convert to fraction form
    1,005.21/1,387.09 = 690.75/x
  3. Step 3: Cross multiply
    1,005.21x = 1,387.09 × 690.75
  4. Step 4: Simplify right side
    1,005.21x = 958,123.76
  5. Step 5: Solve for x
    x = 958,123.76/1,005.21
  6. Step 6: Final answer
    x = 953.16

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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.