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Finding the Fourth Proportional to 987.90, 1,361.86 and 777.68

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Solution

The fourth proportional to 987.90, 1,361.86 and 777.68 is: 1,072.06

Step by Step Solution

  1. Step 1: Write the proportion equation
    987.90 : 1,361.86 = 777.68 : x
  2. Step 2: Convert to fraction form
    987.90/1,361.86 = 777.68/x
  3. Step 3: Cross multiply
    987.90x = 1,361.86 × 777.68
  4. Step 4: Simplify right side
    987.90x = 1,059,091.28
  5. Step 5: Solve for x
    x = 1,059,091.28/987.90
  6. Step 6: Final answer
    x = 1,072.06

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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.