Answer :
30. Since there are twice as many children as adults, let's say the number of adults is x. That means the amount of children is 2x. You know that in total there are 45 people. This means that the number of adults plus the number of children is 45. So we can set up x + 2x = 45. We can solve for x. 3x = 45 so x = 15. Remember, as we stated before, x is the number of adults. 2x is the number of children. Since x = 15, 2x = 30 so there are 30 children in the group.