Home / 15.21-21-13.40

Finding the Fourth Proportional to 15.21, 21 and 13.40

Calculator

Solution

The fourth proportional to 15.21, 21 and 13.40 is: 18.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    15.21 : 21 = 13.40 : x
  2. Step 2: Convert to fraction form
    15.21/21 = 13.40/x
  3. Step 3: Cross multiply
    15.21x = 21 × 13.40
  4. Step 4: Simplify right side
    15.21x = 281.40
  5. Step 5: Solve for x
    x = 281.40/15.21
  6. Step 6: Final answer
    x = 18.50

Related Problems

Find fourth proportional to 7.61, 10.50 and 6.70
Half scale
Find fourth proportional to 30.42, 42 and 26.80
Double scale
Find fourth proportional to 16.21, 22.38 and 14.40
Similar ratio
Find fourth proportional to 22.82, 31.50 and 20.10
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.