BEATCALC:  Beat the Calculator!

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From B. Lee Clay


 Squaring Numbers

 Multiplying Numbers

 Dividing Numbers

 Adding Numbers

  1. even numbers 2 through selected 2-digit evens
  2. digits of square of repeating ones
  3. consecutive odds
  4. consecutive between 2 numbers
  5. sequence from 1 to selected 2-digit number
  6. sequence from 1 to selected 1-digit number and back
  7. sequences in the 10's
  8. sequences in the 20's
  9. sequences in the 30's
  10. sequences in the 40's
  11. sequences in the 50's
  12. sequences in the 60's
  13. sequences in the 70's
  14. sequences in the 80's
  15. series of doubles
  16. series of quadruples
  17. series of 10 numbers

 Subtracting Numbers

  1. 1's repeating, divide by 9, subtract 21
  2. 8's repeating, divide by 9, subtract 10
  3. squares of two numbers
  4. reversing/adding/subtracting 3-digit numbers

 Percents

  1. finding 2.5 percent
  2. finding 5 percent
  3. finding 15 percent
  4. finding 20 percent
  5. finding 25 percent
  6. finding 33 1/3 percent
  7. finding 40 percent
  8. finding 45 percent
  9. finding 55 percent
  10. finding 60 percent
  11. finding 70 percent
  12. finding 75 percent

Calculation
Practice Exercises

Full List



   Add sequences of numbers in the 70's

  1. Choose a 2-digit number in the 70's. To add all the 70's
    from 70 up through this number and down from it:
  2. Square the 2nd digit of the number
    (keep the carry)   _ _ X
  3. The number of terms is 2 × the 2nd digit + 1.
  4. Multiply the number of terms by 7 (+ carry)   X X _

   Example:

  1. If the 2-digit number in the 70's selected is 73:
    (70 + 71 + 72 + 73 + 72 + 71 + 70)
  2. Square the 2nd digit of the number:
    3 × 3 = 9   _ _ 9
  3. No. of terms = 2 × 2nd digit + 1:
    2 × 3 + 1 = 7
  4. 7 × no. of terms: 7 × 7 = 49   4 9 _
  5. So the sum of the sequence is 499.

   See the pattern?

  1. If the 2-digit number in the 70's selected is 78:
    (70 + 71 + 72 + ... + 78 + 77 + ... 72 + 71 + 70)
  2. Square the 2nd digit of the number:
    8 × 8 = 64 (keep carry 6)  _ _ 4
  3. No. of terms = 2 × 2nd digit + 1:
    2 × 8 + 1 = 17
  4. 7 × no. of terms: 7 × 17 + 6 = 49 + 6 =
    119 + 6 = 125   1 2 5 _
  5. So the sum of the sequence is 1254.
     


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19 July 1999
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