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Multiply by 11 board for 72 times 11
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5 Mental Math Tricks for Faster Calculations

Pick one shortcut and run a two-minute drill.

April 10, 2026Math Gym Team1 min read

Try the shortcut

Multiply by 11 without a column setup

Keep the outside digits, add the middle pair, then carry only if needed.

Multiply by 11 board for 72 times 11
  1. 1Place the first digit, 7.
  2. 2Add the two digits for the middle: 7 + 2 = 9.
  3. 3Place 2, then check against 72 x 10 + 72.
Why it works

Multiplying by 11 is multiplying by 10 and adding the original number once more.

Carry check

Bridge a sticky addition through ten

When the units feel crowded, complete ten first and carry only the leftover part.

Bridge-to-ten board for 7 plus 8
  1. 1Use 3 from 8 to make 10.
  2. 2Keep the leftover 5 visible.
  3. 3Read 10 + 5 = 15.
When to use it

Use complements when a units carry is likely but the next ten is easy to reach.

Shortcuts are useful only when the first move is obvious.

Promise

Practice one pattern at a time: times 11, ending-in-5 squares, round-adjust, percentage flip, or subtract-by-adding.

Worked Example

For 85 x 11, keep 8 and 5, add the middle 8 + 5 = 13, carry 1 left, and read 935.

Mistake to Avoid

Do not collect five tricks and drill none of them. A shortcut becomes useful after repeated examples, not after reading the rule once.

Practice Drill

Choose one trick. Do ten examples, review misses, then stop before the method gets sloppy.

Recap

The useful part is reducing small pauses. Pick the matching category and stay on one level until the first move feels obvious.