Question

7*RCA EDUCATION*
*ALLIGATION*
*9749176587*
400 students appeared in an examination. 60% of the boys and 80% of the girls passed the examination. If the total
appered percentage is 65%, how many girls appeared in the examination :-
In what proportion must tea at Rs. 12.45 per kg be mixed with tea at 16.95 per kg, so that the mixture be worth Rs.
14.55 per kg :-
. Gold is 19 times as heavy as water and copper 9 times. In what ratio these metals be mixed so that the mixture may
be 15 times as heavy as water :-
50 kg of sugar divided into two parts, first part sold at a profit of 14% and second part sold at a loss of 6%. On the
whole there is 4% loss observed. How much quantity was sold at profit :-
5. A sum of Rs. 625 is made up 80 notes which are either 10 Rs. or 5 Rs. How many there are each kind :-
A sum of Rs. 1500 is lent out into two parts one at 8% another at 6%. If the total annual interest is Rs. 105, find the
money lent at 8% :-
The population of a town is 8000. If the male population increased by 6% and the female population increased by
10%, then the total population becomes 8600. Find the original numbers of female in the town-​

Answer 1

Answer:

1) Let's put this in equations first. Suppose x is the number of girls, and y is           the number of boys that participated.

Then we know that  

400 = x + y    -  (1)

Also, we know that 260 people passed the exam (260 = 0.65 * 400)

In that 260, we know we have 60% of all the boys, so 0.60 * y and also 80% of all the girls, so 0.80 * x.

That gives us:

260 = 0.8 * x + 0.6 * y     -  (2)

Rewriting (1) tells us

y = 400 - x       - (3)

We can substitute y in (2) by this, so we rewrite to:

260 = 0.8 * x + 0.6 * (400 - x)

Now we just solve for y:

260 = 0.8 * x + 240 - 0.6 * x

260 = 0.2 * x + 240

20 = 0.2 * x

100 = x

So now we know that there were 100 girls that participated in the exam.