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Finding the Fourth Proportional to 991.95, 1,368.89 and 643.24

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Solution

The fourth proportional to 991.95, 1,368.89 and 643.24 is: 887.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    991.95 : 1,368.89 = 643.24 : x
  2. Step 2: Convert to fraction form
    991.95/1,368.89 = 643.24/x
  3. Step 3: Cross multiply
    991.95x = 1,368.89 × 643.24
  4. Step 4: Simplify right side
    991.95x = 880,524.80
  5. Step 5: Solve for x
    x = 880,524.80/991.95
  6. Step 6: Final answer
    x = 887.67

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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.