A series of Multiplication Tricks

1. Multiply by 5: Multiply by 10 and divide by 2.
2. Multiply by 6: Sometimes multiplying by 3 and then 2 is easy.
3. Multiply by 9: Multiply by 10 and subtract the original number.
4. Multiply by 12: Multiply by 10 and add twice the original number.
5. Multiply by 13: Multiply by 3 and add 10 times original number.
6. Multiply by 14: Multiply by 7 and then multiply by 2.
7. Multiply by 15: Multiply by 10 and add 5 times the original number, as above.
8. Multiply by 16: You can double four times or you can multiply by 8 and then double the result.
9. Multiply by 17: Multiply by 7 and add 10 times original number.
10. Multiply by 18: Multiply by 20 and subtract twice the original number.
11. Multiply by 19: Multiply by 20 and subtract the original number.
12. Multiply by 24: Multiply by 8 and then multiply by 3.
13. Multiply by 27: Multiply by 30 and subtract 3 times the original number.
14. Multiply by 45: Multiply by 50 and subtract 5 times the original number.
15. Multiply by 90: Multiply by 9 (as above) and put a zero on the right.
16. Multiply by 98: Multiply by 100 and subtract twice the original number.
17. Multiply by 99: Multiply by 100 and subtract the original number.