## BEATCALC:  Beat the Calculator!

Back to Calculation Tips & Tricks

 From B. Lee Clay

Squaring Numbers

Multiplying Numbers

Dividing Numbers

Subtracting Numbers

Percents

Calculation
Practice Exercises

Full List

### Add a sequence from one to a selected              2-digit number

1. Choose a 2-digit number.
2. Multiply the 2-digit number by half the next number, or
Multiply half the 2-digit number by the next number.

#### Example:

1. If the 2-digit even number selected is 51:
2. The next number is 52. Multiply 51 times half of 52.
3. 51 × 26: (50 × 20) + (50 × 6) + 1 × 26) =
1000 + 300 + 26 = 1326
4. So the sum of all numbers from 1 through 51 is 1326.

See the pattern?

1. If the 2-digit even number selected is 34:
2. The next number is 35. Multiply half of 34 × 35.
3. 17 × 35: (10 × 35) + (7 × 30) + (7 × 5) =
350 + 210 + 35 = 560 + 35 = 595
4. So the sum of all numbers from 1 through 34 is 595.

With some multiplication practice you will be able to find these sums of sequential numbers easily and faster than someone using a calculator!