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

Add sequences of numbers in the 20's
 Choose a 2digit number in the 20's. To add all the 20's
from 20 up through this number and down from it:
 Square the 2nd digit of the number
(keep the carry) _ _ X
 The number of terms is 2 × the 2nd digit + 1.
 Multiply the number of terms by 2 (+ carry).
X X _
Example:
 If the 2digit number in the 20's selected is 23:
(20 + 21 + 22 + 23 + 22 + 21 + 20)
 Square the 2nd digit of the number: 3 × 3 = 9
_ _ 9
 No. of terms = 2 × 2nd digit + 1: 2 × 3 + 1 = 7
 2 × no. of terms: 2 × 7 = 14
1 4 _
 So the sum of the sequence is 149.
See the pattern?
 If the 2digit number in the 20's selected is 28:
(20 + 21 + 22 ... + 28 + 27 + ... 22 + 21 + 20)
 Square the 2nd digit of the number: 8 × 8 = 64
(keep carry 6) _ _ 4
 No. of terms = 2 × 2nd digit + 1: 2 × 8 + 1 = 17
 2 × no. of terms (+ carry): 2 × 17 + 6 = 40
4 0 _
 So the sum of the sequence is 404.
