SOLUTION: In a school 50% of the students are younger than 10, 1/20 are 10 years old and 1/10 are older than 10 but younger than 12, the remaining 70 students are 12 years or older. How man

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Question 1055591: In a school 50% of the students are younger than 10, 1/20 are 10 years old and 1/10 are older than 10 but younger than 12, the remaining 70 students are 12 years or older. How many students are 10 years old?
Answer by ikleyn(52781)   (Show Source): You can put this solution on YOUR website!
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In a school 50% of the students are younger than 10, 1/20 are 10 years old and 1/10 are older than 10 but younger than 12,
the remaining 70 students are 12 years or older. How many students are 10 years old?
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Let x = the total number of students in the school.

Then 0.5x are those who are younger than 10;       (1)

     0.05 are 19 years old;                        (2)

     0.1x are older than 10 but younger than 12.   (3)


Their sum (1) + (2) + (3) is 0.5x + 0.05x + 0.1x = 0.65x.


The remaining are x - 0.65x = 0.35x,  and the equation is

0.35x = 70.


Then x =  = 200.

Thus there are 200 students in the school.

Hence, 10-years old student's population is 0.1*200 = 20.


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