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3 times even number

Rules:

a. Write half of the multiplier and put 0 at the end.

b. Double the multiplier and subtract it from Rule (a).

Examples:

3 x 2; Half of 2 is 1. Put 0 at the end to form 10. Take away twice the multiplier.
Twice of 2 is 4. 10-4 = 6. Therefore 3 x 2 = 6.

3 x 4; Half of 4 is 2. Put 0 at the end to form 20. Take away twice the multiplier.
Twice of 4 is 8. 20-8 = 12. Therefore 3 x 4 = 20.

3 x 12; Half of 12 is 6. Put 0 at the end to form 60. Take away twice the multiplier.
Twice of 12 is 24. 60-24 = 36. Therefore 3 x 12 = 36.


3 time odd number

Rules:

a. Write half of the multiplier (odd number by 2  you get decimal)

b. Ignore the decimal point and write the number  down.

c. Double the multiplier and subtract it from Rule  (b).

Examples:

3 x 1; Half of 1 is 0.5. Ignore the decimal decimal point to get 5.
Double of 1 is 2. 5 - 2 = 3. Therefore 3 x 1 = 3.

3 x 7; Half of 3 is 3.5. Ignore the decimal decimal point to form 35.
Double of 7 is 14. 35 - 14 = 21. Therefore 3 x 7 = 21

3 x 19; Half of 19 is 9.5. Ignore the decimal point to form 95.
Double of 19 is 38. 95 - 38 = 57.  Therefore 3 x 19 = 57.