Almost all basic concepts required on GMAT Quant section are covered in the following videos.
Work Rates
[youtube]https://www.youtube.com/watch?v=Sc1MpH2bDv4[/youtube]
Union and Intersection of Sets
[youtube]https://www.youtube.com/watch?v=ktav02fitiQ[/youtube]
Sets
[youtube]https://www.youtube.com/watch?v=mgGiqsnb9xw[/youtube]
Motion
[youtube]https://www.youtube.com/watch?v=-lMTbML86l4[/youtube]
Geometry – Symmetry
[youtube]https://www.youtube.com/watch?v=lNGZbajRfaQ[/youtube]
Geometry – Spheres
[youtube]https://www.youtube.com/watch?v=HozOG8e0tD0[/youtube]
Geometry – Rectangular Solids
[youtube]https://www.youtube.com/watch?v=SJycga8V02M[/youtube]
Multiplying Decimals
[youtube]https://www.youtube.com/watch?v=GsL39QrqPKw[/youtube]
Intersecting Lines and Figures
[youtube]https://www.youtube.com/watch?v=iX1rDRKSVfA[/youtube]
Dividing Fractions
[youtube]https://www.youtube.com/watch?v=9fE6MCD_Lzk[/youtube]
Geometry – Diagonals
[youtube]https://www.youtube.com/watch?v=F5zDDgUs70k[/youtube]
Decimal or Percentage Expressions of Probability
[youtube]https://www.youtube.com/watch?v=PZ6TgH7UWbI[/youtube]
Geometry – Cylinders
[youtube]https://www.youtube.com/watch?v=tWHxuw9xQsU[/youtube]
Problem Solving - Circles -- GMAT Pill
[youtube]https://www.youtube.com/watch?v=51P-ww1bils[/youtube]
Adding and Subtracting Decimals
[youtube]https://www.youtube.com/watch?v=IavJlscG60w[/youtube]
Square Roots
[youtube]https://www.youtube.com/watch?v=d0ScfdcfJxU[/youtube]
Permutations vs. Combinations -- GMAT Pill
[youtube]https://www.youtube.com/watch?v=MbzqmEH4SlA[/youtube]
Solving Simultaneous Equations using Substitution
[youtube]https://www.youtube.com/watch?v=qx1vkRVpbPY[/youtube]
Solving Linear Equations with One Variable
[youtube]https://www.youtube.com/watch?v=CKLU_LrRKHs[/youtube]
Slope of a Line
[youtube]https://www.youtube.com/watch?v=q6qLOsFhZv4[/youtube]
Negative Bases
[youtube]https://www.youtube.com/watch?v=PhfMHo3JTRo[/youtube]
Fractional Exponents
[youtube]https://www.youtube.com/watch?v=hvEJrp9UzQo[/youtube]
Variables
[youtube]https://www.youtube.com/watch?v=229MTmwxwXc[/youtube]
Percents in the Answer Choices
[youtube]https://www.youtube.com/watch?v=02jCcEchlBs[/youtube]
The Data Sufficiency Question Type
[youtube]https://www.youtube.com/watch?v=Puo6Ja9HBG8[/youtube]
Number Properties
[youtube]https://www.youtube.com/watch?v=3FrJfs59kHM[/youtube]
Calculation vs. Conceptualization
[youtube]https://www.youtube.com/watch?v=XA3MYXP31_s[/youtube]
Combining Statements in Data Sufficiency
[youtube]https://www.youtube.com/watch?v=5-a0eZpoO5o[/youtube]
More on Picking Numbers
[youtube]https://www.youtube.com/watch?v=sHaLGB5ytVo[/youtube]
Strategic Guessing: Elimination
[youtube]https://www.youtube.com/watch?v=h4psEqWOOTQ[/youtube]
Fractions and Decimals
[youtube]https://www.youtube.com/watch?v=1pJ-g9MUewc[/youtube]
Equations
[youtube]https://www.youtube.com/watch?v=qIFZ4fOQ8Q4[/youtube]
Circles
[youtube]https://www.youtube.com/watch?v=CuGbgZIekKA[/youtube]
Inequalities
[youtube]https://www.youtube.com/watch?v=t9E7c25C-w4[/youtube]
Quadratic Equations
[youtube]https://www.youtube.com/watch?v=FmFJG8JeQkk[/youtube]
Probability
[youtube]https://www.youtube.com/watch?v=aWlekctXiZ8[/youtube]
Rates and Speed - Converting Rates
[youtube]https://www.youtube.com/watch?v=5lW-1fWSgws[/youtube]
Geometry - Multiple Figures
[youtube]https://www.youtube.com/watch?v=td15KTZrngg[/youtube]