Home / 28.32-39-21

Finding the Fourth Proportional to 28.32, 39 and 21

Calculator

Solution

The fourth proportional to 28.32, 39 and 21 is: 28.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    28.32 : 39 = 21 : x
  2. Step 2: Convert to fraction form
    28.32/39 = 21/x
  3. Step 3: Cross multiply
    28.32x = 39 × 21
  4. Step 4: Simplify right side
    28.32x = 819
  5. Step 5: Solve for x
    x = 819/28.32
  6. Step 6: Final answer
    x = 28.92

Related Problems

Find fourth proportional to 14.16, 19.50 and 10.50
Half scale
Find fourth proportional to 56.64, 78 and 42
Double scale
Find fourth proportional to 29.32, 40.38 and 22
Similar ratio
Find fourth proportional to 42.48, 58.50 and 31.50
1.5x scale

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.