A) 10
B) 90
C) 100
D) 110
Correct Answer: C
Solution :
Let the number of students in three classes be 2x, 3x and 5x respectively. According to the question, \[\text{(}2x+30\text{)}:(3x+20)::(5x+\text{ }20)\] = 4 : 5 : 7 \[\Rightarrow \] \[\frac{2x+20}{3x+20}=\frac{4}{5}\] \[\Rightarrow \] \[10x+100=12x+80\] \[\Rightarrow \] \[2x=20\] \[\Rightarrow \] \[x=10\] Total number of students in the beginning \[=2x+\text{ }3x+5x\] \[=10x=10\times 10=100\]You need to login to perform this action.
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