Ex: 47
Step1: Look for the nearest 10 boundary.
3 from 47 to 50
Step2: Since we went up 3 to 50, now go down 3 from 47 to 44.
Step3: Now mentally multiply 44 x 50 = 2200 - 1st answer.
Step4: 47 is 3 away from the 10 boundary 50, Square 3 as 9 - 2nd answer.
Step5: Add the first and second answer, 2200 + 9
Ans: 2209
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