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?
we know that students that are younger than 10--------------------------------------------------> 50% students that are 10 years old-------> 1/20----> 0.05-----------------------------> 5% students that are older than 10 but younger than 12----> 1/10---> 0.10----> 10% -------------------------------------------------------------------------------------------------------------- total of 65% remaining=100%-65%-----> 35% the remaining 70 students are 12 years or older so 35%=70 students
by proportion 70/35%=x/100%-----> x=100*70/35-----> x=200 students total students=200
students that are 10 years old-------> 0.05*200-----> 10 students
