Assorted Multiplication Rules

Multiply any number by 5: Multiply any number by 10 and divide by 2.

Multiply any number by 9: Multiply any number by 10 and subtract the original number.

Multiply any number by 6: Sometimes multiplying by 3 and then 2 is easy.

Multiply any number by 12: Multiply any number by 10 and add twice the original number.

Multiply any number by 13: Multiply any number by 3 and add 10 times original number.

Multiply any number by 14: Multiply any number by 7 and then Multiply any number by 2

Multiply any number by 15: Multiply any number by 10 and add 5 times the original number, as above.

Multiply any number by 16: You can double four times, if you want to. Or you can multiply by 8 and then by 2.

Multiply any number by 17: Multiply any number by 7 and add 10 times original number.

Multiply any number by 18: Multiply any number by 20 and subtract twice the original number.

Multiply any number by 19: Multiply any number by 20 and subtract the original number.

Multiply any number by 27: Multiply any number by 30 and subtract 3 times the original number.

Multiply any number by 45: Multiply any number by 50 and subtract 5 times the original number.

Multiply any number by 90: Multiply any number by 9 and put a zero on the right.

Multiply any number by 98: Multiply any number by 100 and subtract twice the original number.