Multiply with a working base like 50

From the sub-sutra Ānurūpyeṇa, Proportionately, in Bharati Krishna Tirtha's 1965 book Vedic Mathematics. Deep dive into the sub-sutra

Try it with your numbers

First number Second number

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When to use it

Both numbers sit near 20, 30, 40, 50 ... like 46 × 43 or 52 × 48.

The idea

Use a working base such as 50 = 5 × 10. Do the near-base trick from 10, then multiply the left part by 5.

Worked example: 46 × 43

1. 46 +6
   43 +3Working base 40 = 4 × 10. 46 is +6 and 43 is +3 from it.
2. 196 | Cross: 46 + 3 = 49. Scale by 4: 49 × 4 = 196.
3. 196 | 18 → 1978Right part: +6 × +3 = 18. Combine: 196 × 10 + 18 = 1978.

Practice this trick

All 15 speed tricks, each with its calculator. The speed tricks use sutras from Bharati Krishna Tirtha's 1965 book Vedic Mathematics; the lessons, problems and pictures here are our own.