In large bowl, beat cake mix, bananas, oil, water and eggs with electric mixer on low speed 30 seconds. Beat on medium speed 2 minutes, scraping bowl occasionally until smooth. Place 1 3/4 cups batter into each round cake pan. Spoon remaining batter into 6 lined muffin cups. Bake round cake 35 to 40 minutes and cupcakes 18 to 23 minutes or until toothpick inserted in cake comes out clean. Cool 10 minutes; remove from pans to cooling rack. Cool completely, about 30 minutes.