Final answer:
Jump bands were popular in the 40s and 50s because they played jazz and attracted young, hip, and white audiences. They also contributed to the blurring of racial lines in the 1950s. Rock 'n' roll, a genre influenced by jump bands, offered an escape from the dominant culture and became a symbol of rebellion for the youth.
Step-by-step explanation:
Jump bands were extremely popular in the 40s and 50s because they played jazz music that attracted large audiences of young, hip, and white individuals called flappers and sheiks. These bands, particularly the Black jazz bands like the King and Carter Jazzing Orchestra, gained immense popularity among white urbanites in the 1920s. Rock 'n' roll also played a significant role in blurring racial lines and bringing white and black teenagers together through social interactions in the 1950s. This genre of music offered a temporary escape from the dominated culture of affluent white America and became a symbol of rebellion for the youth of that era.