The average age of boys in a class is 15.4

Question

The average age of boys in a class is 15.4, while that of girls in the same class is 14.4. If the average of the class is 14.8, what is the ratio of boys to girls in the class?
A) 1:3
B) 1:2
C) 2:1
D) 2:3
E) 3:2

PareshGmat · Accepted Answer

Answer = D = 2:3

Simple Method (Using Alligation)

Avg Boys ............... Avg Girls

15.4 ........................ 14.4

................ 14.8 .............. (Class Avg)

= (14.8-14.4=0.4) ................ = (15.4-14.8 = 0.6)

Ratio = \frac{0.4}{0.6} = \frac{2}{3}

PareshGmat · Answer

Algebric Method:

Let the number of boys = x

\frac{b_1 + b_2 + ..... + b_x}{x} = 15.4  ................... (1)

Let the number of girls = y

\frac{g_1 + g_2 + ........ + g_y}{y} = 14.4  .................. (2)

Class average  = \frac{b_1 + b_2 + ........ +b_x + g_1 + g_2 + ..... + g_y}{x+y} = 14.8  ............... (3)

Placing values of (1) and (2) in equation (3)

\frac{15.4x + 14.4y}{x+y} = 14.8

\frac{x}{y} = \frac{2}{3}

Answer = D

Celestial09 · Answer

Hi!
Experts : chetan4u , bunuel , magoosh, empowergmat, ... i tried to solve ad took 2 mins 20 seconds.. 
made estimate as ration of girls has to be higher .. reason: weight is inclined towards girls..
rest solved three option.
kindly share some other quick method which can save time please.
Thnaks

gracie · Answer

let b=#boys
g=#girls
15.4b+14.4g=14.8(b+g)
b/g=2/3
b:g=2:3

Abhishek009 · Answer

154b + 144g = 148 ( b + g )

154b + 144g = 148b + 148g

Or,  154b - 148b = + 148g - 144g

Or,  6b = 4g

Or,  \frac{b}{g} = \frac{4}{6}  =  2:3

Hence, correct aswer will be (D)  2:3

kanusha · Answer

Boys Avg age : 15.4 = 15 + 0.4
Girls Avg age : 14.4 = 14 + 0.4
I assumed
Boys : Girls = 15x : 14x 
x = 4
60 : 70
6:7
I just choose 2:3

Can i solve something like this?
However, other's explanations make sense
Thanks

stonecold · Answer

Excellent Question  chetan2u

Here is my approach -->
Let the number of Boys be  B 
Let the number of Girls be  G 
Hence we need  B:G

Sum(Age's of all boy's)=>  15.4B 
Sum(Age's of all Girl's)= 14.4G

Now 
Mean of the total class =>  \frac{15.4B+14.4G}{B+G} =14.8 
Hence  0.6B=0.4G 
or \frac{B}{G}= \frac{2}{3}

Hence the Ratio=>  2:3

Hence D

jasro815 · Answer

This can be solved using a line

Avg (Boys) = 15.4 , Avg (Girl) = 14.4 , Avg (Class) = 14.8

14.4..14.6.. 14.8 ..15.0..15.2..15.4

Parts in ratio for girls = 14.8-14.4 = 0.4
Parts in ratio for girls = 14.8-15.4 = 0.6

\frac{0.4}{0.6} =  \frac{2}{3}

Since the class average is closer to girls average, their weightage is higher. Reverse the fraction which is now the ratio 2:3

ShankSouljaBoi · Answer

used alligations criss cross method:

B G

AV

15.4 14.4

14.8

Subtract diagonally

.4 .6

so B/G = .4/.6 = 2/3 = Answer

KanishkM · Answer

KeyWord: boys to girls in the class

Boys------------Girls
15.4------------14.4
---------14.8------
0.4------------0.6

2-------------3

D

bumpbot · Answer

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The average age of boys in a class is 15.4

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