# 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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then 50% of x=x/2

1/20 of x=x/20

1/10 of x =x/10

remaining 70 students .

now we have ,

x/2=x/20+x/10+70

LCM of 20 and 10=20

x/2={(x+2x)/20}+70

x/2=3x/20+70

x/2=(1400+3x)/20

20x=2{(1400+3x)}

20x=2800+6x

20x-6x=2800

14x=2800

x=2800/14

x=200.

number of 10 year old students are = x/20

=200/20

=10.