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Finding the Fourth Proportional to 1,987.60, 2,981.70 and 688.90

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Solution

The fourth proportional to 1,987.60, 2,981.70 and 688.90 is: 1,033.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,987.60 : 2,981.70 = 688.90 : x
  2. Step 2: Convert to fraction form
    1,987.60/2,981.70 = 688.90/x
  3. Step 3: Cross multiply
    1,987.60x = 2,981.70 × 688.90
  4. Step 4: Simplify right side
    1,987.60x = 2,054,093.13
  5. Step 5: Solve for x
    x = 2,054,093.13/1,987.60
  6. Step 6: Final answer
    x = 1,033.45

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1.5x scale

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.