In a group of students, mean weight of boys is 80 kg and mean weight of girls is 50 kg. If the mean weight of all the students taken together is 60 kg, then the ratio of the number of boys so that of girls is

Question

In a group of students, mean weight of boys is 80 kg and mean weight of girls is 50 kg. If the mean weight of all the students taken together is 60 kg, then the ratio of the number of boys so that of girls is (A) 2: 1 (B) 1: 2 (C) 2: 3 (D) none of these

Tardigrade Admin · Accepted Answer

Let the number of boys be n1 and that of girls be n2, then 60 = (80n1 + 50n2/n1+n2) ⇒ 60n1 + 60n2 = 80n1+50n2 ⇒ 10n2= 20n1 ⇒ n1: n2: : 1 :2

Q. In a group of students, mean weight of boys is 80 kg and mean weight of girls is 50 kg. If the mean weight of all the students taken together is 60 kg, then the ratio of the number of boys so that of girls is

2 : 1

1 : 2

2 : 3

none of these

Let the number of boys be $n_{1}$ and that of girls be $n_{2}$ , then
$60 = \frac{80 n _{1} + 50 n _{2}}{n _{1} + n _{2}}$
$\Rightarrow 60 n_{1} + 60 n_{2} = 80 n_{1} + 50 n_{2}$
$\Rightarrow 10 n_{2} = 20 n_{1} \Rightarrow n_{1} : n_{2} :: 1 : 2$

Q. In a group of students, mean weight of boys is 80 kg and mean weight of girls is 50 kg. If the mean weight of all the students taken together is 60 kg, then the ratio of the number of boys so that of girls is

2 : 1

1 : 2

2 : 3

none of these

Let the number of boys be n1​ and that of girls be n2​, then 60=n1​+n2​80n1​+50n2​​ ⇒60n1​+60n2​=80n1​+50n2​ ⇒10n2​=20n1​⇒n1​:n2​::1:2

Let the number of boys be $n_{1}$ and that of girls be $n_{2}$ , then
$60 = \frac{80 n _{1} + 50 n _{2}}{n _{1} + n _{2}}$
$\Rightarrow 60 n_{1} + 60 n_{2} = 80 n_{1} + 50 n_{2}$
$\Rightarrow 10 n_{2} = 20 n_{1} \Rightarrow n_{1} : n_{2} :: 1 : 2$