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19. Two-thirds of children are in the age group 1-12 yr. Of this, if three-fourths are in the age group of 1-8 yr. Find the fraction of children in the age group of 9-12 yr? RRB NTPC (Phase 1) 2016 (1) 1/3 (2) 1/4 (3) 1/6 (4) 1/2

11th - 12th Class
Maths
Solution
109
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19. (3) Let the number of total children ( =x ) Number of children in ( 1-12 ) yr age group ( =frac{2}{3} x ) ( therefore ) Number of children in ( 1-8 ) yr age group ( =frac{2}{3} x times frac{3}{4}=frac{x}{2} ) Then, Number of children in ( 9-12 ) yr age group [ =frac{2 x}{3}-frac{x}{2}=frac{4 x-3 x}{6}=frac{x}{6} text { or } frac{1}{6} text { th } ] of total children.