: Help..............In a school a certain number of boys and girls attend a certain examination. The mean mark of the boys was 40 and the mean mark of the girls was 60.Mean of all students is 48.Find the number of boys and girls in a class of 100.

Question

: Help..............In a  school a certain number of boys and girls attend a certain examination. The mean mark of the boys was 40 and the mean mark of the girls was 60.Mean of all students is 48.Find the number of boys and girls in a class of 100.

wasiqss · Answer

(40x+60y)/100=48
x+y=100

wasiqss · Answer

solve two simoultaneous eq

wasiqss · Answer

boys r 60, galx 100

king · Answer

not possible sorry wrong answer x+y needs to be 100

wasiqss · Answer

sorry i mean to say galx 40

wasiqss · Answer

typed wrong

king · Answer

oh ok but how did u get first two equations....xplain

king · Answer

sry only first equation

wasiqss · Answer

listen what will be mean of marks?
total marks divided by candidate

king · Answer

and what is x and what is y?

wasiqss · Answer

x is boys , y is number of galx

king · Answer

yeah but how 40 * x and 60 * y?

wasiqss · Answer

so the total marks is number of boys into their marks+number of galx nto their mean marks then divided by total number of students that s 100

wasiqss · Answer

ok

king · Answer

why is 40 multiplied by x and 60 multiplied into y?

wasiqss · Answer

40 is the mean marks of boys and x is the total number of boys in class and y is total number of gals ad 60 is the mean marks of gal

king · Answer

yeah so  why do we multiply?

king · Answer

why do we multiply?

king · Answer

why do we multiply?

king · Answer

anwar help?

anonymous · Answer

OK. Let $n$ and $m$ be the number if boys and girls respectively, then $40 n$ is the total points that boys scored, and $60m$ is the total of the girls. We can then write $\frac{40n+60m}{m+n}=48$. We also have $m+n=100$. Solve them to find m and n.

wasiqss · Answer

we multiply to get the total number of marks 
like suppose there are 3 students in class and their mean mark is 90
so how we will get the marks obtained by class in total as in we want to add the marks of all the student

anonymous · Answer

If you solve them, you will get $n=70 \text{ boys, and } m=30 \text{ girls}$.

king · Answer

no anwar u are wrong

king · Answer

wasiq why will we multiply if 3 students are there then mmean is x1+x2+x3/3=90

anonymous · Answer

Oh sorry, I solved them for $46$, not $48$. Wait a sec.

anonymous · Answer

60 boys and 40 girls :)

king · Answer

yea anwser is rite but i dont understand why we multiply...

asnaseer · Answer

the mean of the these 3 numbers: 12,14,16 is calculated as:$$\frac{12+14+16}{3}=\frac{42}{3}=14$$the total of those 3 numbers is: 12+14+16=42, which is the same as the mean times the number of numbers you have: 14*3=42

wasiqss · Answer

king u r dumb, sorry to say bt tru

asnaseer · Answer

so, if you are given the mean and the number of items, you can always work out the total number of items as (mean)*(number of items)

anonymous · Answer

Let me explain it to you. Assume we have 5 students, and their mean is 50. We can write that as $\large{\frac{x_1+x_2+x_3+x_4+x_5}{5}=50}$. Now if we want to find the sum of the points that all the 5 student scored, we just multiply both sides by $5$ to get $\large {x_1+x_2+x_3+x_4+x_5=5\times 50}$. Makes sense?

asnaseer · Answer

sorry "the total of all the items"

king · Answer

oh ok thnx anwar and asnaseer
thnk u very much

asnaseer · Answer

no problem - always glad to help