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Stage 12 of 20

Two-Digit Addition (With Carry)

The most common real-world addition scenario: two two-digit numbers where carrying is required. Master the left-to-right method with mid-problem carries.

What You'll Learn

  • Carry from ones to tens during two-digit addition
  • Handle chains where tens also overflow into hundreds
  • Maintain accuracy under time pressure

Explanation

For 38 + 47: ones give 8 + 7 = 15. Write 5, carry 1. Tens: 3 + 4 + 1 = 8. Answer: 85.

Left-to-right with adjustment: 38 + 47 → 38 + 40 = 78, then 78 + 7 = 85.

When tens also carry (68 + 75), the hundreds digit appears. Ones: 8+5=13 (carry 1). Tens: 6+7+1=14. Answer: 143.

Round-and-adjust works well: 38 + 47 ≈ 40 + 45 = 85. Small adjustments from rounding cancel out.

Pro Tips

  • • Always process ones first internally, even when adding left-to-right — you need the carry ready.
  • • Estimate the answer to catch errors: 38 + 47 is between 70 and 90.
  • • Practice the hardest combinations: both ones digits are 6 or greater.

Practice Exercises

Work through each problem mentally. Click "Show Answer" when you're ready to check.

  1. 1. 38 + 47 = ?
  2. 2. 56 + 39 = ?
  3. 3. 67 + 28 = ?
  4. 4. 45 + 38 = ?
  5. 5. 59 + 27 = ?
  6. 6. 48 + 36 = ?
  7. 7. 75 + 19 = ?
  8. 8. 68 + 25 = ?
  9. 9. 57 + 48 = ?
  10. 10. 39 + 56 = ?