21. the answer is...

four hundred thirty-five (435)

The House of Representatives is the larger chamber of Congress. Since 1912, the House of Representatives has had 435 voting members. However, the distribution of members among the states has changed over the years. Each state must have at least one representative in the House. Beyond that, the number of representatives from each state depends on the population of the state. The Constitution says that the government will conduct a census of the population every 10 years to count the number of people in each state. The results of the census are used to recalculate the number of representatives each state should have. The total number of voting U.S. representatives does not change.