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

Adding consecutive numbers between two
numbers
Choose two 2digit numbers less than 20
(no limits for experts).
Add all the numbers between them:
 Add the numbers;
 Subtract the numbers and add 1;
 Multiply half the sum by this difference + 1, OR
Multiply the sum by half the difference + 1.
Example:
 If the two numbers selected are 6 and 19:
 Add the numbers: 6 + 19 = 25.
 Subtract the numbers: 19  6 = 13. Add 1: 13 + 1 = 14.
 Multiply 25 by half of 14: 25 × 7 = 175.
 So the sum of the numbers from 6 through 19 is 175.
See the pattern?
 If the two numbers selected are 4 and 18:
 Add the numbers: 4 + 18 = 22.
 Subtract the numbers: 18  4 = 14. Add 1: 14 + 1 = 15.
 Multiply half of 22 by 15: 11 × 15 = 165 (10 × 15 + 15).
 So the sum of the numbers from 4 through 18 is 165.
Practice with examples restricted to less than 20, then advance to larger numbers.
You will impress your friends when you beat the calculator.
