SUTRA:- The sutra is applicable only if it fulfills two conditions. First, the sum of unit digits in multiplicand and multiplier should be 10. And second, the remaining digit/s in both the multiplicand and multiplier are same.
EXAMPLE 1:- 32 × 38
SOLUTION: – The answer will be obtained in two parts (left part & right part).
STEP 1 – Since the sum of the digits in unit place of both numbers is 10, multiply them to get the right part of the answer.
2 × 8 = 16
STEP 2 – The remaining digits are same. Multiply the remaining digit by the successor of it to get the left part of the answer.
3 (remaining digit) × 4 (successor of remaining digit)
3 × 4 = 12
Hence, 32 × 38 = 1216
EXAMPLE 2 – Find the product of 61 and 69.
SOLUTION:- The answer will be obtained in two parts (left part & right part).
STEP 1 – Since the sum of the digits in unit place of both numbers is 10, multiply them to get the right part of the answer.
1 × 9 = 9
STEP 2 – The remaining digits are same. Multiply the remaining digit by the successor of it to get the left part of the answer.
6 (remaining digit) × 7 (successor of remaining digit)
6 × 7 = 42
Hence, 61 × 79 = 4209 (treat 9 as 09)
EXAMPLE 3 – Find the product of 124 and 126.
STEP 1:- 4 × 6 = 24 (Multiplying the digits in one’s place)
STEP 2:- 12 × 13 = 156 (Multiplying the remaining number by its successor)
Answer:- 15624
NOTE:-First, try to be good at looking at the numbers to be multiplied and find out whether the numbers are fulfilling the required conditions.