Squaring Numbers
Multiplying Numbers
Dividing Numbers
Adding Numbers
 even numbers 2 through selected 2digit evens
 digits of square of repeating ones
 consecutive odds
 consecutive between 2 numbers
 sequence from 1 to selected 2digit number
 sequence from 1 to selected 1digit number and back
 sequences in the 10's
 sequences in the 20's
 sequences in the 30's
 sequences in the 40's
 sequences in the 50's
 sequences in the 60's
 sequences in the 70's
 sequences in the 80's
 series of doubles
 series of quadruples
 series of 10 numbers
Subtracting Numbers
 1's repeating, divide by 9, subtract 21
 8's repeating, divide by 9, subtract 10
 squares of two numbers
 reversing/adding/subtracting 3digit numbers
Percents
 finding 2.5 percent
 finding 5 percent
 finding 15 percent
 finding 20 percent
 finding 25 percent
 finding 33 1/3 percent
 finding 40 percent
 finding 45 percent
 finding 55 percent
 finding 60 percent
 finding 70 percent
 finding 75 percent
Calculation
Practice Exercises
Full List

Subtract
from a repeating 1's number, divide
by
9, subtract 21
 Select a number between 2 and 10 digits made up of 1's.
 Subtract a number equal to the number of digits in the number you have selected.
 Divide by 9. The answer will have one less digit than the original number in
the series 123456789.
 Subtract 21.
Example:
 If the repeating number selected has 5 digits:11111:
 Subtract 5 (same as number of digits) and divide by 9. The answer will be 1234
(4 digits).
 Subtract 21: 1234  21 = 1213.
 So (111115)/9  21 = 1213.
See the pattern?
 If the repeating number selected has 8 digits:11111111:
 Subtract 8 (same as number of digits) and divide by 9. The answer will be 1234567
(7 digits).
 Subtract 21: 1234567  21 = 1234546.
 So (111111118)/9  21 = 1234546.
For those who enjoy extensions of these patterns:
(answers after the division by 9, step 3)
11 digit number, answer is 1234567900
12 digit number, answer is 12345679011
13 digit number, answer is 123456790122
14 digit number, answer is 1234567901233
15 digit number, answer is 12345679012344
and ?
Extend the exercises using this basic pattern by changing step 4 to add or subtract
other numbers.
