Most recent trick: multiplying two two-digit numbers in your head.
Ex:
46
x 35
Steps:
1. Multiply the two tens digits together. (4x3=12 and remember it)
2. Cross multiply twice (the top tens by bottom ones digit and vice versa) and ADD THOSE TWO PRODUCTS together and hold it.(4x5=20 and 6x3=18 so 20+18=38)
3. Do the "new addition" of the two stored red numbers by adding the tens digit of the 38 (so 3) to the 12 and you get 15 and just tack on the 8, so the new stored number is 158.
4. Multiply the two ones digits together (6x5=30 and take that product and do the "new addition" to 158. Remember add the tens place of the 30 (JUST 3) to 158 = 161 and tack on the ZERO.
5. New answer = 1610....pretty cool!!!!
You'll be able to amaze everyone you know by telling them the
DAY OF THE WEEK for any given DATE in history!!!
Follow these steps like Mr. Byster showed us in class.
YOU ALWAYS NEED THIS CHART:
Jan 1
Feb 4
Mar 4
Apr 0
May 2
June 5
July 0
Aug 3
Sept 6
Oct 1
Nov 4
Dec 6
Sun 1
Mon 2
Tues 4
Wed 5
Thurs 7
Fri 8
Sat-no remainder
**THIS ONLY WORKS FOR the 1900s..
*For this example I will use the date of November 30, 1976.
1. Take the last two digits of the year (76)
2. Multiply it by 1.25 (95)
3. Get rid of everything to the right of the decimal (still just 95, but if it carried out to some decimal places, drop them here)
4. Add the month CODE from above (Nov. = 4, so 95+4=99)
5. Add the date (99+30=129)
6. Divide by 7 (129/7=18.4285...)
7. Read the # in the TENTHS place (4) and match that up with the day of the week from the above chart....4=Tuesday.