Multiply by 11

What This Drill Trains

The ×11 pattern is a classic mental math crowd-pleaser, but it is also a serious fluency tool. Two-digit numbers times 11 appear in mental estimates and Vedic-style work. This drill is where you prove the split-and-add method under a timer instead of only watching a demonstration.

How to Think During the Round

For a two-digit number ab (value 10a + b), write a, then a+b, then b. If a+b is 10 or more, carry 1 to the hundreds place. Example: 45 × 11 → 4, 4+5=9, 5 → 495. Example with carry: 78 × 11 → 7, 7+8=15, 8 → write 5 and carry 1 → 858.

You have 60 seconds. Accuracy still outranks raw speed: one calm method repeated well beats a streak of guesses. After the timer ends, notice which problems felt sticky — that short review is where real improvement happens.

Worked Examples

Study these before you press Start. Try to recreate the thinking without looking at the answer first.

Common Mistakes

• Forgetting to carry when the middle sum is 10 or greater.
• Writing digits in the wrong order (ending with the tens digit).
• Applying the two-digit pattern blindly to three-digit numbers without extending the method.

Practice Tips

• Always compute the middle sum before writing any digit.
• Verify with (n × 10) + n when you distrust a carry.
• Read the Multiply by 11 lesson once if carries still feel surprising.

Suggested Session Plan

1. Read the method section once if this skill is new.
2. Cover the answers and re-solve the three worked examples aloud.
3. Start the timed round and stick to one strategy.
4. Replay once, then write down any fact or pattern you missed.
5. If the same error repeats, open the full lesson for more examples and a practice set with an answer key.

Full explanation, extra worked examples, and practice problems for this skill: open the related stage lesson .

Prefer a structured curriculum instead of random drills? Browse all learning stages or read the complete mental arithmetic guide . More timed drills live on the games hub.