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Linear Equations in One Variable

SAT Math· difficulty 5/5

In a class, the ratio of girls to boys is 5:45:4. After 66 more boys join, the ratio becomes 5:65:6. How many girls are in the class?

  • A

    10

  • B

    20

  • C

    15

    check_circle
  • D

    12

Explanation

Let girls =5k= 5k, boys =4k= 4k. After: 5k4k+6=56\frac{5k}{4k + 6} = \frac{5}{6}, so 30k=20k+3030k = 20k + 30 and k=3k = 3. Girls =15= 15.

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