When 12 marbles are added to a rectangular aquarium, the water in the aquarium rises 1 1/2 inches. in total, how many marbles must be added to the aquarium to raise the water 2 3/4 inches?

21 marbles would be added to raise the water 2 3/4 inches

Step-by-step explanation:

When 12 marbles are added to a rectangular aquarium, the water in the aquarium rises 1 1/2 inches. Converting 1 1/2 inches to improper fraction, it becomes 3/2 inches

Let x represent the number of marbles that would be added to the aquarium to raise the water 2 3/4 inches. Converting 2 3/4 inches to improper fraction, it becomes 11/4 inches. Therefore

12 marbles = 3/2 inches rise

x marbles = 11/4 inches rise

Cross multiplying,

12 × 11/4 = 3/2 × x

33 = 3x/2

3x = 33 × 2 = 66

x = 66/3 = 21

the first one is x^2+2x+2

the second one is x^2+4

the last one is x^2-4x+8

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