Home / 860.40-1,290.40-421.21

Finding the Fourth Proportional to 860.40, 1,290.40 and 421.21

Calculator

Solution

The fourth proportional to 860.40, 1,290.40 and 421.21 is: 631.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    860.40 : 1,290.40 = 421.21 : x
  2. Step 2: Convert to fraction form
    860.40/1,290.40 = 421.21/x
  3. Step 3: Cross multiply
    860.40x = 1,290.40 × 421.21
  4. Step 4: Simplify right side
    860.40x = 543,532.77
  5. Step 5: Solve for x
    x = 543,532.77/860.40
  6. Step 6: Final answer
    x = 631.72

Related Problems

Find fourth proportional to 430.20, 645.20 and 210.61
Half scale
Find fourth proportional to 1,720.80, 2,580.81 and 842.42
Double scale
Find fourth proportional to 861.40, 1,291.90 and 422.21
Similar ratio
Find fourth proportional to 1,290.60, 1,935.61 and 631.82
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.