Show Menu
Cheatography

GMAT QUANTITATIVE SECTION

Algebra

ax2+bx+c
sum roots: -b/a
Δ =b2-4ac
product roots: c/a

Ratios

q1 : q2 = q2-final : q1-final
num<denum so fracti­on<1 so (x+1)/­(y+1) > x/y
num>denum so fracti­on>1 so (x+1)/­(y+1) < x/y
from exerci­se: a-10 + b-20 + c-15 = 11k + 18k + 24k so 1105-4­5=53k (ratios gains)
effica­cy=1/t (inverse propor­tio­nna­lity)
1/t1 : 1/t2 : 1/t3
take LCM = k so you have k/t1 : k/t2 : k/t3
compute to get x : y : z form
then do x + y + z and cross product
Rate of interest = intere­stp­ery­ear­/pr­inc­ipa­lin­vested * 100
When compared, use compared amount as the base
so you have Δ / base * 100
Use quantity as unit of q, the percentage change is
Δ = increased or decrease quantity
Δ/1(or­iginal amount) * 100
To make a profit, take initial price and add the desired profit so that: new price per unit = initial (1+pro­fit)
Always find a 100 that makes the calcul­ation easy = if it's not marked price it's cost price etc.
On Y1, simple and compound interests are the same
Find interest rate w/ difference and interest on interest
Interest = principal * rate * time
discount of marked price = discount / marked price * 100
Usually, these questions include:
1. ratios of shared amounts,
2. time to perform a task,

3. invest­ments and interests
4. price increases or decreases
=> FOR PROFITS
 

Number properties

remainder of sum = sum of remainders
remainder of product = product of remainders
nb of trailing zeros = at least nb of 5s
number of factors = product of each power + 1 [ex: 120 -> 23*­5*­3-> (1+1)­*(1­+1)­*(3+1) = 16]
from exerci­se: If remainder of product to find, can work by pairs
If two expres­sions are equal, the exponents must be equal (if 2n+2m = 23m-1 then n+2m = 3m-1)
AP Sum of arithmetic progre­ssion = (1st + Last / 2) * nb of terms
AP nth term → an = a1 + (n-1) * d (common divisor)
AP sum of the n first terms : n/2 [2a1 + (n-1)d]
GP sum of first n terms = a(rn-1) / r-1where r is common ratio
Number of ways of selecting two distinct integers from the set of first 100 positive integers = 100C2 ways.
i.e., 100C2 = 100 × 992

Sets

P(AUB) = P(A) + P(B) - P(A∩B)
P(AUBUC) = P(A) + P(B) + P(C) + P(A∩B∩C) - [P(A∩B) + P(A∩C) + P(B∩C)]

Statistics and Average

Standard deviation = mean -> (numbe­r-m­ean)2 -> mean -> square root(mean)

From video

Work and Rate
R=J/T
machines identi­ques: nR=J/T
 

Geometry / Coordinate Geometry

air triangle = 1/2 * products of sides * sin (inside angle)
sin 150° = 1/2
sum of interior angles of polygon = (n-2)*180
Pythag­orean triplets (c is odd, at least 2 prime numbers, 1 even number): (3,4,5) / (5,12,13) / (7,24,25) / (8,15,17) / (9,40,41) / (11,60,61) / (12,35,37)
area triangle = r (inserted circle) * semi-p­eri­meter triangle
equation of a circle center (a,b): (x-a)2 + (y-b)2 = r2
equation of a line that crosses two interc­epts: x/value x + y/value y = 1 so (value x)y + (value y)x = (value x)(value y)
       

Help Us Go Positive!

We offset our carbon usage with Ecologi. Click the link below to help us!

We offset our carbon footprint via Ecologi
 

Comments

No comments yet. Add yours below!

Add a Comment

Your Comment

Please enter your name.

    Please enter your email address

      Please enter your Comment.

          Related Cheat Sheets

          Weights and Measures Cheat Sheet