Use Google.

The GMAT is a computer based test and consists of four sections. An Analytical Writing Assessment, which gives you 30 minutes to write an essay analyzing an argument. A Integrated Reasoning section, which requires that you analyze multiple forms of information and ask questions about it this is also 30 minutes. The main portion of the exam, what makes up your total score from 200-800 consists of a 75 minute quantitative section and a 75 minute verbal section. The quantitative section has two different kinds of questions, data sufficiency and problem solving. The verbal section had three different kinds of questions, critical reasoning, reading comprehension and sentence correction.

For details follow the link on mba.com, the official GMAT site
http://www.mba.com/india/the-gmat-exam/gmat-exam-format-timing.aspx