Simplify the following text for a Grade 3 native English-speaking person.
Original: The 2009 census put the population at more than 39 million people . The population of metropolitan Khartoum ( including Khartoum , Omdurman , and Khartoum North ) is growing rapidly and is estimated at about five to seven million , including around two million displaced persons from the southern war zone as well as western and eastern drought-affected areas .
Simplified: About 4 million of these live in Khartoum or in towns that are joined to it .