A bag contains yellow, green, blue, and white marbles. The ratio of yellow, green, blue, and white marbles is 1:2:3:4. If the bag contains 180 marbles, then how many blue marbles are there?
ratio of yellow, green, blue, and white marbles is 1:2:3:4, so ratio of blue marbles to total marbles is 3:(1+2+3+4)=3:10
x: the total number of blue marbles
3/10 = x/180
multiplying both sides by 180,
x = 54
