Mental Math Tricks to Try
Trick #1:
MEMORY WIZARD Tell your friend that you are able to memorize a 26 digit number.
1. Write the number: 35 831 459 437 077 415 617 853 819
on a piece of paper and show it to your friend.
2. On another piece of paper, draw 26 blank lines for the digits of the
number and then proceed to write down the number.
3. You do not need to memorize the number. Just remember the first two
digits, 35, and then add to get the remaining 24 digits. The next
digit is the sum of the last two digits. If the sum is greater than
10, use just the final digit of the sum for the next digit.
Trick # 2:
MAGIC ELEVENS
When multiplying any two digit number by 11 1. the last digit of the number is the last digit of the answer
2. add the two digits to find the middle digit of the answer
3. the first digit of the number (plus any carry from the middle sum) is
the first digit of the answer
4. Example: 24 X 11: the last digit is 4, the middle digit is 6 and the
first digit is 2, so 24 X 11 equals 264.
Trick # 3:
QUICK THINKING
1. You can be the first to calculate sums in your head when you use the
‘quick think’ method.
2. Try to add the digits from left to right in your head, rather than from
right to left as you often do when you write them down.
3. When you add the right-hand digits in your head, if the sum is 10 or
bigger, just mentally add a ten to the sum of the left-hand digits and
then say the answer.
4. For example: 46 + 34 can be calculated using Quick Think, by adding 40
+ 30 in your head and thinking 70, and then adding 6 + 4 and thinking
10. (Adding on the one ten) you get 70 (+ 10) = 80 plus 0. So . . .
your answer is 80.
5. Of course, another way to do this using mental math is to see that 46
is 4 away from 50, so if you take the 4 from 34, you will get 50 + 30 =
80.
Instructions: Practise these tricks with your partner
using questions you make up yourself. See who can
come up with the answers first! Discuss what you did.