In a school, the ratio of the number of large classrooms to small classrooms is 3:4. If the number of small rooms is 20, then find the number of large rooms.


Ratio of number of large classrooms to small classrooms = 3:4


Number of small classrooms = 20


ratio = =


=


Cross multiply we get


Number of large classrooms = = 3 × 10


Therefore, number of large classrooms is 30


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