In a school 3/7 of the students are girls. If there are 240 boys, find the numbers of girls in the school.
In a school 3/7 of the students are girls. If there are 240 boys, find the numbers of girls in the school.
Short method,
There are 3 / 7 girls in a school
so, 4 / 7 are boys given as 240
One part = 240 / 4 = 60
therefore 3 one part =60 * 3 = 180
There is 3/7 girls = 180
Another method
Let the number of Students in a school be x.
Thus,Number of Girls = 3/7 of the total Students
= 3/7 of x
= 3x/7
We know,
Number of Boys + Number of Girls = Total Students.
240 + 3x/7 = x
240 = x - 3x/7
240 = (7x - 3x) /7 [Taking L.C.M.]
240 × 7 = 4x
x = 60 × 7
x = 420
Total number of Students in a school is 420.
Thus, Number of Girls = 3/7 × x
= 3/7 × 420
= 180
Thus, the number of Girls in a school is 180
Short method,
There are 3 / 7 girls in a school
so, 4 / 7 are boys given as 240
One part = 240 / 4 = 60
therefore 3 one part =60 * 3 = 180
There is 3/7 girls = 180
Another method
Let the number of Students in a school be x.
Thus,Number of Girls = 3/7 of the total Students
= 3/7 of x
= 3x/7
We know,
Number of Boys + Number of Girls = Total Students.
240 + 3x/7 = x
240 = x - 3x/7
240 = (7x - 3x) /7 [Taking L.C.M.]
240 × 7 = 4x
x = 60 × 7
x = 420
Total number of Students in a school is 420.
Thus, Number of Girls = 3/7 × x
= 3/7 × 420
= 180
Thus, the number of Girls in a school is 180
