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Finding the Fourth Proportional to 1,987.56, 2,980.62 and 690.12

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Solution

The fourth proportional to 1,987.56, 2,980.62 and 690.12 is: 1,034.93

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,987.56 : 2,980.62 = 690.12 : x
  2. Step 2: Convert to fraction form
    1,987.56/2,980.62 = 690.12/x
  3. Step 3: Cross multiply
    1,987.56x = 2,980.62 × 690.12
  4. Step 4: Simplify right side
    1,987.56x = 2,056,985.47
  5. Step 5: Solve for x
    x = 2,056,985.47/1,987.56
  6. Step 6: Final answer
    x = 1,034.93

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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.