Mental Math Multiplying Tricks
The all famous 11 trick
Somewhere in themathlab.com, locked with a secret password, is a treasure page. This page has over 10 FREE gifts for you. You are now looking at the TREASURE FINDER page that will lead you to this password.

Read through the page below and do what it says. Write down any parts of the password as you find them.

You will need paper and pencil to keep track of your mental math results.

This treasure page's password has ten letters.

The letters match the Password Clues arranged in the order you see below. GOOD LUCK.
6
8
4
9
7
3
2
10
5
1

When you KNOW the password

THE ELEVEN TRICK:

This is our absolute FAVORITE multiplication trick here at themathlab.com. It is a real "show stopper". People will think you are unbelievably smart when they see you do this one.

To multiply any single digit number by eleven you just write the digit twice. Ex. 7x11=77.

The impressive power comes when you can take any two, three, or four digit number times eleven, and get the answer IN YOUR HEAD without showing a scrap of work.

Ex. 23 x 11 = 253 instantly!

Here's how you do it.

Since you are multiplying eleven by 23, your answer will have a 3 on the right and a 2 on the left and the SUM of 2 and 3, which is five, in the middle. Just think of it as pulling the 2 and 3 apart and inserting their SUM in the middle.

Believe it or not, it's just that easy. Any two digit number times eleven can be done like that. If the sum in the middle is 10 or greater just put the ones digit of the sum in the middle and make the left digit bigger by one.

Ex. 48 x 11 = 528 (Think: eight goes on the right, 4+8=12 so write down the two in the center and carry the one to add to the 4 making the leftmost number now a 5.)

Ex. 99 x 11 = 1089

Here. Try a few yourself. Click on the ? to see if you are correct. *This only works in Internet Explorer.

  1. 16 x 11 = ?
  2. 52 x 11 = ?
  3. 11 x 63 = ?
  4. 55 x 11 = ?
  5. 78 x 11 = ?

This method even works for longer numbers. You place the ones digit in the ones spot and simply continue adding pairs across the number from right to left, carrying as needed until the leftmost digit or that digit plus one more is placed on the left side of the answer.

Here. Take a look at couple examples.

Ex. 349 x 11 = 3839 (Think: place the nine on the right first, then add 4+9=13. So we place the three beside the nine, carry the one and add it to 3+4 giving us a total of 8. We write the eight to the left of the three and then since there was nothing to carry, we finish the number by placing the 3 in the leftmost spot.)

Ex. 978 x 11 = 10,758 (Here we have to carry the whole way across the number. That's why the leftmost digit is not nine but 10.)

Try your hand at a few. If you get them all correct, go ahead and tackle the Password Clues.

Remember to click the ? to see if you are correct.

  1. 37 x 11 = ?
  2. 298 x 11 = ?
  3. 5,603 x 11 = ?

PASSWORD CLUES

Mentally use the trick for eleven to multiply the ten problems below.

Write down each answer then look in the DECODER GRID to find which letter corresponds to the problem number.

Then match each letter with its problem number in the password as shown here:
6
8
4
9
7
3
2
10
5
1

  1. 11 x 12 =
  2. 11 x 18 =
  3. 123 x 11 =
  4. 68 x 11 =
  5. 459 x 11 =
  6. 11 x 390 =
  7. 506 x 11 =
  8. 379 x 11 =
  9. 1,234 x 11 =
  10. 3.4 x 11 =

DECODER GRID

748
47.4
5,049
4,169
198
374
208
5,566
s
f
r
e
m
c
b
g
l
5,066
132
4,290
37.4
549
13,574
648
1,353
z
f
d
o
h
i
a
n

 

When you KNOW the password

 

 

 

To learn even more of these mental math tricks try the book cover

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