6,371 views

The pie chart below has the breakup of the number of students from different departments in an engineering college for the year $2012$. The proportion of male to female students in each department is $5:4$. There are $40$ males in Electrical Engineering. What is the difference between the numbers of female students in the civil department and the female students in the Mechanical department?

Number of female students in Electrical = $40\times \dfrac{4}{5} = 32$

Number of female students in Civil = $32\times \dfrac{30}{20} = 48$ (Since proportion of male students to female students is same, the breakup chart is the same for number of female students)

Number of female students in Mechanical = $32\times \dfrac{10}{20} = 16$

So, answer = $48 - 16 = 32$
by

Why divide by 20 while finding number of female students in civil and mechanical?
Since the ratio of m:f is same for all department so ,

Electrical → 20 % -------- 32 females

Civil →        30% -------- ? females, cross multiply to get ?
from the female students of civil , the female students of mechanical =

48 * (10 / 30) = 16
Electrical male students = 40
∴ Electrical female students = 40 × (4/5)= 32
Total no. of students in Electrical department = (40 + 32) = 72 (which is 20% of the total mass)
∴ Total no. of students in the college = 72 × (100/20) = 360
Total no. of students in Civil department = 360 × (30/100) = 108
Civil female students = 108 × (4/9) = 48
Total no. of students in Mechanical department = 360 × (10/100) = 36
Mechanical female students = 36 × (4/9) = 16
∴ Difference = (48 − 16) = 32 (Ans)

nice ..
Good explanation
since electrical is 20%,first find out how many female using 40/5=8,8*4=32 for mechanical is 10% so that (if 20% means 32,from that 10% means 16) similarly civil is 30% so that (16*3=48) 48-16=32
by

Gr8...