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In Mrs. Craig's statistics class there are twice as many 11th grade students as there are 9th and 10th grade students combined. There are twice as many 12thgrade students as 9thgrade students, and the number of 11thgrade students is ten times the number of 12thgrade students. If there are 32 students altogether in Mrs. Craig's statistics class, how many 12thgrade students are there?

 Mar 17, 2018
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Let the number of 9th grade students = N

Let the number of 10th grade students = T

Then the number of 11th grade students = 2[N+T]

The number of 12th grade students = 2N

2[N+T] = 10[2N]................................(1)

N + T + 2[N+T] + 2N = 32................(2), solve for N, T

N = 1 - number of students in 9th grade.

T = 9 - number of students in 10th grade.

2[1+9] = 20 - number of students in 11th grade.

2 x 1 = 2 - number of students in 12th grade.

 Mar 17, 2018

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