Of a group of boys and girls at Central Middle School’s after-school party, 15 girls left early to play in a volleyball game. The ratio of boys to girls then remaining was 2 to 1. Later, 45 boys left for a football game. The ratio of girls to boys was then 5 to 1. How many students attended the party?

  90

Step-by-step explanation:

Let g and b represent the number of girls and boys attending, respectively.

After 15 girls left, the ratio of boys to girls was ...

  b/(g -15) = 2/1

  b = 2g -30 . . . . . multiply by (g-15)

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After 45 boys left, the ratio of girls to boys was ...

  (g -15)/(b -45) = 5/1

  g -15 = 5b -225 . . . . . . multiply by (b-45)

  g = 5b -210

Using the latter to substitute into the former, we have ...

  b = 2(5b -210) -30

  450 = 9b . . . . . add 450-b

  50 = b . . . . . . 50 boys attended

  g = 5(50) -210 = 40 . . . . . 40 girls attended

The number of students who attended the party was 50 +40 = 90.

Check

After 15 girls left, the ratio of boys to girls was 50/25 = 2/1.

After 45 boys left, the ratio of girls to boys was 25/5 = 5/1.

(-1,-0.5)

step-by-step explanation:

b is the right answer