CSAT DAILY MISSION #49

Jul 4, 2015

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Over the past few days, we have been moving the time of publishing of the CSAT Mission here and there to figure out if publishing at 11 am is the best timing, and if that is when most people are responding. Please expect this jiggery-pokery to go on for a couple more days. The Mission has reached its mid-point, BTW. So, congratulations, you have completed 50% of your CSAT preparation. Expect the most familiar type of questions asked by UPSC to get a little repeated from now on.

Question 1

A census taker approaches a house and asks the woman who answers the door “How many children do you have and what are their ages?” The woman says “I have three children, the product of their ages is 36 and the sum of their ages is my house number”. The census taker notes down the house number and asks for more information when a shout shout from inside the house comes “Mom! Where are you?”. The woman says “That is my eldest child calling me” and the census taker says “OK. Thank you. I now have the ages of your kids”.
What are the ages of the kids?

(A) 9 years, 2 years , 2 years

(B) 6 years, 6 years , 1 year

(D) 6 years, 3 years , 2 years

Question 2

A person covers 18 km along a stream in 4 hours and the same distance against the stream in 12 hours. What is the speed of the stream in km/hr?

(A) 1

(B) 1.5

(D) 2

Question 3

The HCF and LCM of two numbers are 21 and 4641 respectively. If one of the numbers lies between 200 and 300, what is the other number?

(A) 315

(B) 399

(D) 353

Question 4

What value will come in place of the question mark?

(A) 12

(B) 8

(D) 16

Question 5

Out of nine people, eight spent Rs. 30 on average on a meal. The ninth spent Rs.20 more than the average of all the nine. What is the total amount spent by all the people in rupees?

(A) 303.50

(B) 280

(D) 310

SOLUTIONS TO DAILY CSAT MISSION # 50

1.(D) 2.(C) 3.(C) 4.(C) 5.(B)

Explanations
1. On Saturday, no details are given for any gate apart from P. U could be open or closed, and following U, T could be open or closed. R,S,T and U could all be open satisfying all the given conditions while proving option (A) wrong. Since only one of P,Q or R can stay open at any point of time, obviously two gates are always closed at all times. And this proves option (B) wrong. On any weekday, P and S could be open while Q,R,T and U could all be closed. This scenario satisfies all conditions given but disproves option (C).

2. If no govt employee is corrupt, no govt employee from Tina’s family will be corrupt either.

3. and 4. E is second from top, and A is next to it. Two cases can arise here depending on whether A is above E or below E:

Since there are two books between B and D (with D on top), there is only one way D and B can be arranged in each case. In the first case, D and B will be third from top and sixth from top respectively. In the second case, D and B will be first from top and fourth from top respectively. All conditions have been satisfied so far in both cases and neither has been ruled out.

Since there are two books between A and F, F is inserted into the fourth position from top and sixth position from top in the two cases respectively. Then, C is inserted into the only remaining positions on either stack: at the position fifth from top. The two cases that satisfy all conditions are:

3. C is second from bottom in either case.

4. BCF is a continuous series of books in either case.

5. Let the first bottle be 40 litres and the second bottle be 30 litres. Milk was filled to half i.e. 20 litres in the first bottle, and to a third i.e. 10 litres in the second bottle. Total milk = 30 litres. Total volume of the two bottles = 70 litres. So, water = 40 litres. Ratio = 3:4.

Comments

12 responses to “CSAT DAILY MISSION #49”

Nidhi

July 17, 2015

CBCBC
M2K

July 5, 2015

–
B
C
B
C
Admin 2

July 5, 2015

@ Ashwani: In question 1, The maturity factor cannot really be taken into account here. Even a six year old can call to his mother “Mom, where are you?”. So we cannot judge from the voice/tone/words. See the solution in Mission # 48. You have to arrive at the solution using reasoning.
In question 2, what are the two speeds you have calculated to be 4.5 and 1.5? They are speeds of the man and stream only. Stop right there, because this is what has been asked. Why go into more complexity?
In question 3, we agree, your method is better. But we aren’t sure if it can be applied to very large numbers (lets say LCM is 42375 and HCF is 125 or something like that). But let us look into this and we’ll drop you a mail if we find any problem with your method. You continue using it.
Ashwin

July 5, 2015

@ Rishabh correct. It was a pure typo error.
Aamir Khan

July 5, 2015

Plz increase the number of questions. As just 5 are not enough.
puja

July 5, 2015

1.-
2. B
3. –
4. B
5. C
Naveen Shekhar

July 5, 2015

1.#
2.B
3.#
4.B
5.C
shivam

July 4, 2015

4/July/2015
1) a
2) b
3) a
4) b
5) c
Ashwani Bhati

July 4, 2015

Answers are:
A
D
A
B
C

Hmm. So now let me explain.
1). Some might think that the information given is not enough to find the answer!
But its actually quite easy to get the solution.
The reason I “THINK” the answer should be A is because as soon as the child call his mother, its quite understandable that he/she is quite mature. So now his age must be above five. Also, the point to be considered is that we don’t have enough information to find the other age. Hence, other two must be twins. Now we have only options A and B available. But the catch here is as the child called his mother she immediately recognized his/her voice, this implies that elder child must not have a twin. Hence the answer is A.

2). It’s quite simple calculate the two speeds which are 4.5km/h and 1.5km/h. Now the relative speed will give the speed of the stream, which is (4.5-1.5)/1.5 = 2km/h. [Not sure about this though! 🙂 ]

3).
LCM= 52920 = (2)^3 x 3^3 x 5 x 7^2
HCF= 21=3 x 7.
Let the no.s be A and B.
Now the no.s must be = HCF(=21) x some other subset of factors of LCM.
We have,
315 = 3^2 x 5 x 7 = HCF x 15
399 = 3 x 7 x 19 (But 19 is not in factors of LCM)
357= 3 x 7 x 17 (But 17 is not in factors of LCM)
353= Other factors > 21.
So the answer must be A i.e 315.

4). Notice the column Entries!
In each column we have the pattern : “Divide 4th element with 3rd, that will give you product of 1st and 2nd element”.
e.g 64/2 = 32 = 4 x 8.

Hence we get ? = 336 / (7 x 6) = 8.

5).Quite easy, doesn’t need any explanation! 🙂
Rishabh Singh

July 4, 2015

C/D..B..*..B..C
IN Q.3
If hcf and lcm are 21 & 52920 and one no. lies b/w 200 & 300 then only 2 conditions are satisfying it
1)21 × 52920 = 210 × 4410
2)21 × 52920 = 294 × 3780

I dnt understand how @Ashwin selected 315 as the answer.
Renesh

July 4, 2015

1. (not B)
2. B
3. A
4. B
5. C

For que 1, without knowing the house number, how can we choose the correct answer among options A, C and D.
B is definitely not the answer as option B has two children with max age, but the woman said her ELDEST son was calling. That means B is not the answer. But which is the correct among A,C,D ?? 🙁
Ashwin

July 4, 2015

A
B
A
B
C