💡 Tables
19 / 21 near-20 trick
20 ke around — minus ya plus one chunk
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Steps
- 19 × n → pehle 20×n karo, phir n subtract karo.
- 21 × n → pehle 20×n karo, phir n add karo.
- 20 ka table fast hai — isliye yeh trick kaam karti hai.
Worked example
19 × 7 = ?
20×7 = 140, minus 7 = 133
Answer: 133