Misra’s blog

Basic Maths formulaes

Posted by mtwinkle on June 6, 2007

Arithmetic / Properties of Numbers

Even/odd (e/o) identities:

  1. e +/- e = e
  2. e +/- o = o
  3. o +/- e = o
  4. o +/- o = e
  5. e x e = e
  6. e x o = e (also: o x e = e)
  7. o x o = o

Decimal conversions:

  1. ½ = .5
  2. 1/3 = .33, 2/3 = .67
  3. ¼ = .25, ¾ = .75
  4. 1/5 = .2, 2/5 = .4, 3/5 = .6, 4/5 = .8
  5. 1/9 = .11 (repeating), 2/9 = .22 (repeating), etc.
  6. It’s handy to know 6ths, 7ths, and 8ths, but they require more memorization and don’t come up as often.

Percent conversions:

  1. 37% = 0.37 = 37/100
  2. 0.2% = 0.002 = 0.2/100 = 2/1000

Exponents: (note: x^y = “x raised to the y power”)

  1. x^-y = 1/x^y
  2. (x^y)(x^z) = x^(y+z)
  3. (x^y)^z = x^(yz)
  4. x^1/2 = radical (square root of) x.

Radicals (roots): (note: r2 = “radical 2” or “square root of 2”)

  1. r2 = approximately 1.4
  2. r3 = approximately 1.7
  3. Know the square of every integer up to 13.
  4. r(xy) = r(x) times r(y)

Geometry

Area

  1. Triangle: ½ times base times height
  2. Rectangle: length times width
  3. Circle: pi(r^2)

Circumference:

  1. Circle: 2pi(r)
  2. All other figures: the sum of the lengths of all sides

Right triangles:

  1. a^2 + b^2 = c^2, where a and b are two sides of the triangle and c is the hypotenuse (Pythagorean theorem)2.Common integer solutions to the Pythagorean Theorem, including 3 : 4 : 5, 6 : 8 : 10 (and all other multiples of 3 : 4 : 5), and 5 : 12 : 13
  2. The ratio of sides in a triangle with angles 30 : 60 : 90 is x : x(r3) : 2x
  3. The ratio of sides in a triangle with angles 45 : 45 : 90 is x : x : x(r2)

Solids:

  1. Volume: area of the base times height
  2. Surface area: the sum of the areas of all faces of the solid

Coordinate Geometry:

  1. Slope of a line = (change in y)/(change in x)
  2. Equation of a line: y = mx + b, where m = slope and b = y-intercept (the point at which x = 0)

Miscellaneous

  1. Rate = distance/time
  2. Combined work: 1/a + 1/b = 1/t, where a and b are the amount of time it takes two entities working alone to complete a task and t is the amount of time it would take them to complete the task working together. (I’ll go into this in more detail, including some shortcuts, in a future Tip.)
  3. Average = sum of terms / number of terms
  4. Probability = number of desired outcomes / number of possible outcomes

One Response to “Basic Maths formulaes”

  1. Thanks for all your efforts that you have put in this. extremely interesting info. 473806

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

 
%d bloggers like this: