MHB How many girls were there in the class?

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The class initially had 42 pupils, consisting of boys and girls. After 6 boys left, the ratio became three times as many girls as boys remaining. The calculations confirm that there are 27 girls and 9 boys left after the departure of the boys. The initial count included 15 boys and 27 girls, which adds up to the total of 42 students. Therefore, the correct number of girls in the class is 27.
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There were 42 pupils in a class at first. After 6 boys left the class, there were 3 times as many girls as boys. How many girls were there in the class?

My answer: 42 = (x+ 6) + 3x
=> x = 9the (x+6) is basically (boys + 6)

So there are 27 girls and 9 boys? Did I do my work correctly?
 
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I believe that's correct. Another equation we could use is 36 = 3(b - 6) + b - 6. Solving,

36 = 3b - 18 + b - 6
36 = 4b - 24
60 = 4b
b = 15

Then b - 6 = 9 and g = 27, so there are 27 girls in the class.
 
Johnx said:
There were 42 pupils in a class at first. After 6 boys left the class, there were 3 times as many girls as boys. How many girls were there in the class?

My answer: 42 = (x+ 6) + 3x
=> x = 9the (x+6) is basically (boys + 6)

So there are 27 girls and 9 boys? Did I do my work correctly?
It's hard to tell because you start with an equation in "x" but have not said what "x" represents! I presume that you intended x to be the number of boys in the class after the first 6 boys left. The specific question was "How many girls were there in the class?" Yes, there were 27 girls. There were 9 boys left after the first 6 boys left so that there were intially 27 girls and 15 boys in the class. You can check that 27+ 15= 42, the number of students initially in the class.
 
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