Question 970486
.
The ratio of girls to boys in Liza's classroom is 5 to 4. How many girls are in her classroom 
if there is a total of 27 students?
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        It can be solved mentally without using equations.



According to the problem, we can group the students in sets, each containing 5 girls and 4 boys.


Each such group has 5 + 4 = 9 students.


So, the number of such groups is 27/9 = 3.


Thus, the number of girls in the class is 3*5 = 15.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<U>ANSWER</U>


Solved.



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In normal teaching process, the students should learn this grouping method first,
allowing to solve this problem mentally (at 4-th or 5-th grade).


Later, in 6-th or 7-th grade, students will learn proportions and will solve such problems using proportions.


But for normal mathematical development, students should learn the mental solution way first,
using the grouping method.