Are at least 20% of the people in City H who are at least 30

Take population of bilingual to be 1000.
x will be 1250. hence population of people who are atleast 30 years old really depends upon what you assume population of bilingual to be.

I think there is some problem in the red part of the calculation

if there are 100 people atleast 30 years or old, than you can't have 100 men and 100 women.

So let;s take two cases

a> Men = 50, Women = 50
than total# of bilungual people = 0.18*50+0.17*50 = 9 + 8.5 = approx. 18 (that is less than 20)

b> Men = 70, Women = 30
than total# of bilungual people = 0.18*70+0.17*30 = 13 + 6 = approx. 19 (that is less than 20)


So with the assumption, that there are only Male and Female in the city demography, B is sufficient.

I actually didn't get how you got the red part above.

Q: If there are x people who are at least 30, how many of them are bilingual?

1. In City H, 25 percent of the bilingual population is at least 30 years old.

It says just the reverse;
25% of bilinguals are at least 30.

Now, we know neither the total population nor the number of people who are at least 30. We just know that if there are 100 bilinguals among the people in H, 25 of those are at least 30 AND thus, 75 of those are less than 30.

CASE I:
Now, we take non-bilingual into account:
If there are 900 non-bilingual; out of those 900, all are less than 30 AND 0 person or none is at least 30.

Then
Total Population=Bilingual+Non-bilingual=100+900=1000
People who are at least 30= At least 30 among Bilinguals+At least 30 among non-Bilinguals=25+0=25

People who are at least 30= 25
People who are at least 30 AND bilinguals= 25
%=25/25=100%>20%

CASE II:
But, if
If there are 900 non-bilingual; out of those 900, none is less than 30 AND 900 people are at least 30.

Then
Total Population=Bilingual+Non-bilingual=100+900=1000
People who are at least 30= At least 30 among Bilinguals+At least 30 among non-Bilinguals=25+900=25

People who are at least 30= 925
People who are at least 30 AND bilinguals= 25
%=25/925= much less than 20%

We saw two cases:
First, in which % of bilinguals amongst people who are at least 30=100%
Second, in which % of bilinguals amongst people who are at least 30 less than 20%

So, just by knowing that "25 percent of the bilingual population is at least 30 years old" is NOT enough to find whether "at least 20% of the people in City H who are at least 30 years old bilingual". Because, we don't know what's the population, how many are at least 30 etc...

Not Sufficient.

2. In City H, of the population at least 30 years old, 18 percent of the women and 17 percent of the men are bilingual.

Here, we are given ready-made what's been asked. Out of people who are at least 30; 18% bilingual women and 17% bilingual men.

No matter how many people are at least 30 year old; the % of bilinguals(men+women) will always be less than 20; because neither % of men is more than 20 nor that of women is.

e.g.
100 people out of 1million are at least 30.
Out of 100: 90 Men, 10 Women
(0.18*90+0.17*10) will always be less than 0.2(90+10)

x Men, y Women
0.18x+0.17y< 0.2x+0.2y=0.2(x+y)
Sufficient.

Ans: "B"

whoa..good explanation..+1 to you Fluke

Lemme digest it..will get back to you in case required..hehe

2) % of both male & female who are 30yrs old bilingual< 20%.
this % can never be more than 20%. if males are less than 20%, then females have to be more than 20% to cover up.

no need to do any calculation.

Similar question to practice: are-at-least-10-percent-of-the-people-in-country-x-who-are-122734.html

The question is more of logic than of real calculations.

Are at least 20% of the people in City H who are at least 30 years old bilingual?

1. In City H, 25 percent of the bilingual population is at least 30 years old.
The variables here are bilingual population, population >30 yrs and total population.
Say there are 200 bilingual people, so 50 out of them are >30yrs. But >30 yr old is also a variable.
If number of greater than 30 yrs old is 100, answer is yes and if it is 1000, answer is no.
Insufficient

2. In City H, of the population at least 30 years old, 18 percent of the women and 17 percent of the men are bilingual.
The population consists of male and female. And we have % of each.
Therefore, the overall % of people greater than 30 years old who are bilingual will be between the two %, 17% and 18%.
It could be highest 18% when all are women and lowest 17% when all are male.
In whatever be the distribution, the answer is always NO.
Sufficient


B