Latest topics

» Tough Life of a Resin Beadby

**ioncube**Fri Jul 19, 2013 8:16 pm

» Final Year Projects Suggestions

by

**ioncube**Fri Jul 19, 2013 2:48 pm

» Tracking Natural Gas Via Flowmeters

by

**ioncube**Sat Sep 08, 2012 11:04 pm

» Maximising Heat-Transfer Fluid Life

by

**ioncube**Thu Aug 23, 2012 6:16 pm

» Exercise your Brain

by

**ioncube**Thu Jul 19, 2012 12:49 pm

# Exercise your Brain

## Exercise your Brain

**[1] Squaring numbers in the 50's:**

Example 56 x 56:

Step 1: You start out with 25 and add the ones digit to it.

25 + 6 = 31

Step 2: Square the ones digit. 6 x 6 =36 Tack this onto the end of the answer from step 1.

Answer: 56 x 56 = 3,136

Now, if the number from step 2 is less than 10, you have to put a zero in front of it.

So, if it is 53 x 53:

Step 1: 25 + 3 = 28

Step 2: 3 x 3 = 09 (note that since 9 is smaller than 10 we have tu put a zero in front of it)

Answer: 53 x 53 = 2,809

**[2] Squaring numbers that end in 5:**

Example 65 x 65:

Step 1: Take the tens digit and multiply it by the number one greater than it. 6 x 7 = 42

Step 2: Tack 25 onto the end of the number from Step 1.

Answer: 65 x 65 = 4,225

**[3] Multiplying two numbers that end in five that are ten apart:**

Example 65 x 75

Step 1: Take the smaller tens digits (6) and multiply it by one more than the larger tens digit 7+1 = 8 & 6 x 8 = 48

Step 2: Tack 75 on to the end of the number from Step 1.

Answer: 65 x 75 = 4875

**[4] Multiplying two numbers that end in five that are twenty apart:**

Example 65 x 85

Step 1: Multiply the smaller tens digit (6) by one greater than the larger tens digit (8 + 1 = 9) and then add 1 to that product. 6 x 9 = 54. 54 +1 = 55

Step 2: Tack 25 on to the end of the number from Step 1.

Answer: 65 x 85 = 5525

**[5] Multiplying two numbers in the 90's together:**

When you multiply two numbers in the 90's together, in parenthesis next to each number put how far that number is away from 100.

Example: 93 (7) x 96 (4)

Step 1: Add up the numbers in parenthesis 7 + 4 = 11 and subtract that number from 100. 100 - 11 = 89

Step 2: Multiply the two numbers in parenthesis together and tack that on to the number

from Step 1. 7 x 4 = 28

Answer: 93 x 96 = 8928

**[6] Squaring numbers in the 40's:**

Example 43 x 43:

Step 1: You start out with 15 and add the ones digit to it. 15 + 3 = 18

Step 2: You figure out how much the number you are squaring is less than 50 and square that number. 43 is 7 less than 50. 7 x 7 is 49. Tack that number onto the end of the number from step 1.

Answer: 43 x 43 = 1849

Now if the number from step 2 is less than 10, you have to put a 0 in front of it.

Example 48 x 48:

Step 1: 15 + 8 = 23

Step 2: 48 is 2 less than 50. 2 x 2 = 04

Answer: 48 x 48 = 2304

**[7] Multiplying two numbers together between 100 and 109:**

Example: 105 x 107

Step 1: The first digit of the answer is always 1.

Step 2: To get the next two digits of the answer, add the ones digits together. 5 + 7 = 12

Step 3: To get the final two digits of the answer, multiply the ones digits together. 5 x 7 = 35

Answer: 105 x 107 = 11,235

If the number from either step 2 or step 3 is less than 10, you have to put a zero in front of it.

Example: 102 x 104

Step 1: The first digit is always 1.

Step 2: Add the ones digits together. 2 + 4 = 06

Step 3: Multiply the ones digits together: 2 x 4 = 08

Answer: 102 x 104 = 10,608

**[8] Multiplying two numbers together between 200 and 209:**

Example: 204 x 208

Step 1: The first digit is always 4.

Step 2: To get the next two digits of the answer, add the ones digits together and then double it. 4 + 8 = 12, double that is 24.

Step 3: To get the final two digits of the answer, multiply the ones digits together. 4 x 8 = 32

Answer: 204 x 208 = 42,432

If the number from either step 2 or step 3 is less than 10, you must put a zero in front of it.

Example: 205 x 201

Step 1: First digit is 4.

Step 2: 5 + 1 = 6. 6 doubled is 12.

Step 3: 5 x 1 = 05

Answer: 205 x 201 = 41,205

**[9] Squaring Numbers between 491 and 509:**

Example: 494 x 494

Step 1: To get the first three digits of the answer, subtract the number you are squaring by 250. 494 - 250 = 244

Step 2: Tack on a zero to Step 1. So you have 2440.

Step 3: Figure out how far the number you are squaring is away from 500, and square that number and tack it onto the answer from Step 2. 494 is 6 away from 500. 6 x 6 = 36

Answer: 494 x 494 = 244,036

If the number from Step 3 is less than 10, you have to put a zero in front of it.

Example: 503 x 503

Step 1: 503 - 250 = 253

Step 2: Add a zero. You have 2530.

Step 3: 503 is 3 away from 500. 3 x 3 = 09

Answer: 503 x 503 = 253,009

**[10] Multiplying two two digit numbers that end in 1:**

Example: 71 x 61

Step 1: Multiply the tens digits together and tack a zero on at the end. 7 x 6 = 42. Tack on a 0 and you get 420.

Step 2: Add the tens digits together and add that sum to the number from Step 1. 7 + 6 = 13. 420 + 13 = 433

Step 3: Tack a 1 onto the end of the number from Step 2.

Answer: 71 x 61 = 4,331

Example: 31 x 51

Step 1: 3 x 5 = 15. Tack on a zero and you get 150.

Step 2: 3 + 5 = 8. 150 + 8 = 158

Step 3: Tack a 1 onto the end.

Answer: 31 x 51 = 1,581

**ioncube**-

Country :

Posts : 45

Likes Total : 7

Join date : 2012-02-02

Location : Lahore/Faisalabad

Page

**1**of**1****Permissions in this forum:**

**cannot**reply to topics in this forum