Sal works through 155 data sufficiency problems in the GMAC GMAT Review book (so using real GMAT problems). Buy the book, then watch the videos.
1-5, pg. 278.
6-9, pg. 278.
10-15, pgs. 278-279.
16-21, pg. 279.
22-27, pg. 279.
28-32, pg. 280.
33-36, pg. 280.
37-41, pgs. 280-281.
42-46, pg. 281.
47-50, pg. 281.
51-54, pgs. 281-282.
55-58, pg. 282.
59-62, pg. 282.
63-68, pgs. 282-283.
68-72, pg. 283.
73-76, pg. 284.
77-79, pg. 284.
80-83, pg. 284.
84-86, pg. 285.
87-90, pg. 285.
91-94, pgs. 285-286.
95-98, pg. 286.
99-102, pg. 286.
103-106, pg. 287.
107-109, pg. 287.
110-111, pg. 287.
112-115, pg. 287.
116-118, pg. 288.
119-120, pg. 288.
121-124, pg. 288.
125-128, pg. 288.
129-131, pg. 289.
132-134, pg. 289.
135-137, pg. 289.
138-140, pg. 289.
141-142, pg. 289-290.
142-144, pg. 290.
145-147, pg. 290.
148-150, pg. 290.
151-153, pg. 290.
154-155, pg.290.
