22 results for “numbers”
The multiplicative inverse of a number.
The nth root of the product of n numbers.
Powers of complex numbers in trig form.
Closed form for the sum of the first n natural numbers.
Every integer is either even or odd.
Euclid-Euler form of even perfect numbers.
Numbers one less than a power of two.
Numbers of a special exponential form.
Sum of the first n natural numbers.
A Vedic sutra for multiplying numbers close to a base (10, 100, 1000, etc.). Works by finding how far each number is from the base.
A general Vedic multiplication method that works for any two numbers. Uses vertical and crosswise multiplication patterns.
Quick method to square any number near 50 using the identity (50±d)² = 2500 ± 100d + d².
Instantly square any number ending in 5. Multiply the tens digit by (tens digit + 1), then append 25.
Transform numbers with large digits (6-9) into "vinculum" form using complements from 10, making calculations easier.
Use the identity (a+b)(a-b) + b² = a² to square numbers quickly by going to the nearest easy number.
When numbers are near a convenient working base that is a multiple of a power of 10, use a proportional base to simplify the multiplication.
For numbers a little above 100, use the surplus from 100 to multiply almost instantly.
Use (a+1)² = a² + 2a + 1. Square the round number below, add twice it, add 1.
Gauss's formula: the sum of the first n whole numbers is n(n+1)/2 — no adding required.
The sum of the first n odd numbers is always a perfect square, exactly n².
Two numbers equally spaced around a middle value m multiply to m² − d², using the difference of squares.
Multiply miles by 1.6 for km, or divide km by 1.6 for miles. Consecutive Fibonacci numbers are handy approximations.