In The Outsiders when Pony and the rest of the gang were leaving Pony's house, why were they hooting and hollering and doing acrobatics before the...

At the beginning of chapter 9 of The Outsiders, the reader learns the whole gang is jumping around, and doing acrobatics, which they all learned from Darry, as they leave Ponyboy's house for the rumble. They are doing this because they are excited to finally be able to settle the score with the Socs. By winning the fight, the greasers will be able to have their own territory back, and no longer will have...

At the beginning of chapter 9 of The Outsiders, the reader learns the whole gang is jumping around, and doing acrobatics, which they all learned from Darry, as they leave Ponyboy's house for the rumble. They are doing this because they are excited to finally be able to settle the score with the Socs. By winning the fight, the greasers will be able to have their own territory back, and no longer will have to worry about being jumped.

They are also excited to fight as a way to fulfill various needs each of them has and to fit in with the larger group and show their loyalty. This is alluded to by Ponyboy's interview of some of the boys before the fight. His oldest brother Darry for example is teased by Soda when he says Darry likes to fight to "show off his muscles" (Hinton p133), a fact which Darry never denies. Soda also admits to liking to fight himself because "it's a contest" (Hinton p133). Others, such as Two-Bit, like to fight so that they can fit in with the rest of the group. Ponyboy concludes by saying "Soda fought for fun, Steve for hatred, Darry for pride, and Two-Bit for conformity" (Hinton p137). Each of these reasons helps the boys cope with their current situation.

This idea of coping with their situation is also alluded to in a group setting when they proudly sing about being greasers, calling themselves "a menace to society" (Hinton p136). This not only illustrates the theme of loyalty, seen throughout the book, but also shows a sense of pride in belonging to the greaser group despite its disadvantages. It is because of these various reasons that the greasers are excited and are jumping around doing acrobatics when leaving Ponyboy's house before the rumble. 

Hope this helps!