In a recent survey, Q people were asked whether they eat after 22:00

Question

In a recent survey, Q people were asked whether they eat after 22:00 O'clock. 25 percent of the people answered positively and 40 percent of the rest were asked, at what time do they get up in the morning. Which of the following expressions represents the number of people who do not eat after 22:00 and were not asked about the time they get up in the morning?

A. 3Q/20.
B. Q/10.
C. 5Q/9.
D. 3Q/10.
E. 9Q/20.

A. 3Q/20.
B. Q/10.
C. 5Q/9.
D. 3Q/10.
E. 9Q/20.

Nightfury14 · Answer

25% i.e 1/4Q eat dinner after 22:00
3/4Q don't eat dinner after 22:00

\frac{60}{100}*\frac{3}{4}*Q is the answer 
Ans E. 9Q/20.

Good luck
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Turkish · Answer

Q (total) 
 / \
 1Q/4 3Q/4

3Q/4 * 40/100 =3Q/10 were asked, at what time do they get up in the morning. So 7Q/10 were not asked. the number of people who do not eat after 22:00 and were not asked about the time they get up in the morning will be 7Q/10+ 3/4Q = 19Q/20

AbdurRakib · Answer

Actually,  \frac{7Q}{10}  persons  already included  into  \frac{3Q}{4}  persons(already overlapped the quantity).So the highlighted calculations made no sence here.

Please correct me if I miss any point here

IMO ,

The Number of people eat after 22:00= \frac{25Q}{100} = \frac{Q}{4} ,So the number of people DO NOT eat after 22:00=Q- \frac{Q}{4} = \frac{3Q}{4} 
Accordingly,The number of people were asked, at what time do they get up in the morning=  \frac{3Q}{4} * \frac{40}{100} = \frac{3Q}{10} 
The Number of people  eat  after 22:00 and The number of people  were  asked about the time they get up in the morning= \frac{Q}{4} + \frac{3Q}{10} = \frac{11Q}{20}

So,Finally the number of people who  do not  eat after 22:00 and  were not  asked about the time they get up in the morning=Q- \frac{11Q}{20} = \frac{9Q}{20}

Correct Answer E

AmoyV · Answer

Assume Q=100
100-25=75 people said they ate before 22:00
75*0.4=30 people were asked what time they got up in the morning

25+30=55 people were either asked what time they got up in the morning OR ate after 22:00
100-55=45 or 45% of Q were the number of people who did neither.

E is the equation for 45% of Q.

Answer: E

ScottTargetTestPrep · Answer

The number of people who do not eat after 22:00 is 0.75Q. Therefore, 0.4(0.75Q) = 0.3Q people were asked at what time they get up in the morning, and so Q - 0.25Q - 0.3Q = 0.45Q = 9Q/20 people do not eat after 22:00 and were not asked about the time they get up in the morning.

Answer: E

Barca511 · Answer

Does the double matrix method work for this question

Posted from my mobile device

dave13 · Answer

VeritasKarishma  whats wrong with this matrix ?

ShankSouljaBoi · Answer

You are assuming 0 in 2nd coolumn 1st row. You cant use double matrix for this one. Try number picking. Take Q= 100

dave13 · Answer

Thanks, Actually i picked 100 as number and got 0 in 2nd coolumn 1st row. i want to know why it happened so and why do you think matrix wont work for problem like this

ShankSouljaBoi · Answer

Both the events are mutually exclusive... We don't know if both the events are dependent or co dependent , so number picking or algebraic method works best . Also , note that your grid does not take into consideration the fact that the people who have been asked if they wake up in the morning are actually the rest of the people , who did not positively reply to the question >>>>> IF they eat after 22 PM . Check the question stem. Hope this helps

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KarishmaB · Answer

dave13  - Nothing wrong with the matrix. 
You get 45 as those who were not asked and who do not eat after 2200 hrs. 
This means 45% of Q is the answer. That is equal to 9Q/20. 
Answer (E)

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In a recent survey, Q people were asked whether they eat after 22:00

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