Exams


Q:

A potentiometer wire is 100 cm long and a constant potential difference is maintained across it. Two cells are connected in series first to support one another and then in opposite direction. The balance points are obtained at 50 cm and 10 cm from the positive end of the wire in the two cases. The ratio of the emf's is :

A) 3:4 B) 5:4
C) 5:1 D) 3:2
 
Answer & Explanation Answer: D) 3:2

Explanation:

In series : E1 + E2 = K(50)

In parallel : E1 - E2 = K(10)

E1 + E2 / E1 - E2 = 5/1

=> E1/E2 = 3/2

The emf's are in the ratio of 3:2.

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Filed Under: Physics
Exam Prep: AIEEE

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Q:

Three taps P, Q and R can fill a tank in 12 hrs, 15 hrs and 20 hrs respectively. If P is open all the time and Q and R are open for one hour each alternately, starting with Q, then the tank will be full in how many hours ?

A) 9 hrs B) 7 hrs
C) 13 hrs D) 11 hrs
 
Answer & Explanation Answer: B) 7 hrs

Explanation:

Given,

P can fill in 12 hrs

Q can fill in 15 hrs

R can fill in 20 hrs

=> Volume of tank = LCM of 12, 15, 20 = 60 lit

=> P alone can fill the tank in 60/12 = 5 hrs

=> Q alone can fill the tank in 60/15 = 4 hrs

=> R alone can fill the tank in 60/20 = 3 hrs

Tank can be filled in the way that

(P+Q) + (P+R) + (P+Q) + (P+R) + ....

=> Tank filled in 2 hrs = (5+4) + (5+3) = 9 + 8 = 17 lit

=> In 6 hrs = 17 x 6/2 = 51 lit

=> In 7th hr = 51 + (5+4) = 51 + 9 = 60 lit

=> So, total tank will be filled in 7 hrs.

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Filed Under: Time and Work
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11 11476
Q:

In a G - 20 meeting there were total 20 people representing their own country. All the representative sat around a circular table. Find the number of ways in which we can arrange them around a circular table so that there is exactly one person between two representatives namely Manmohan and Musharraf.

A) 2 x (17!) B) 2 x (18!)
C) (3!) x (18!) D) (17!)
 
Answer & Explanation Answer: B) 2 x (18!)

Explanation:

A person can be chosen out of 18 people in 18 ways to be seated between Musharraf and Manmohan. Now consider Musharraf, Manmohan, and the third person, sitting between them, as a single personality, we can arrange them in 17! ways but Musharraf and Manmohan can also be arranged in 2 ways. 

 

Required number of permutations = 18 x (17!) x 2 = 2 x 18!

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Filed Under: Permutations and Combinations
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2 11461
Q:

Ten years ago, Karan was thrice as old as Shiva was but 10 years hence, he will be only twice as old. Find Shiva’s present age ?

A) 70 years B) 30 years
C) 60 years D) 40 years
 
Answer & Explanation Answer: B) 30 years

Explanation:

Let Karan’s present age be x years and Shiva’s present age be y years.
Then, according to the first condition,
x - 10 = 3(y - 10) or x - 3y = - 20 ..(1)
Now, Karan’s age after 10 years = (x + 10) years
Shiva’s age after 10 years = (y + 10)
(x + 10) = 2 (y + 10) or x - 2y = 10 ..(2)
Solving (1) and (2), we get x = 70 and y = 30
Karan’s age = 70 years and Shiva’s age = 30 years.

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Filed Under: Problems on Ages
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Q:

A thief steals half the total number of loaves of bread plus 1/2 loaf from a bakery. A second thief steals half the remaining number of loaves plus 1/2 loaf and so on. After the 5th thief has stolen there are no more loaves left in the bakery. What was the total number of loaves did the bakery have at the beginning ?

A) 21 B) 11
C) 17 D) 31
 
Answer & Explanation Answer: D) 31

Explanation:

Let y be the total number of loaves
a be the remaining loaves after 1st thief
b be the remaining loaves after 2nd thief
and c, d..so on after 3 and 4 th
e = 0 be the remaining loaves after 5th thief

a = y - (y/2 + 1/2)
= y/2 - 1/2

b = a - (a/2 + 1/2)
= a/2 - 1/2

c = b - (b/2 + 1/2)
= b/2 - 1/2

d = c - (c/2 + 1/2)
= c/2 - 1/2

e = d - (d/2 + 1/2)
= d/2 - 1/2
we know that, e = 0,
thus by substitution, we get
d = 1
c = 3
b = 7
a = 15
y = 31
Therefore total number of bread loaves in bakery was 31.

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Filed Under: Numbers
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9 11456
Q:

Which of the following rivers have almost the same point of emerging ?

A) Tapi and Beas B) Brahmaputra and Ganga
C) Indus and Ganga D) Brahmaputra and Indus
 
Answer & Explanation Answer: D) Brahmaputra and Indus

Explanation:
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Filed Under: Indian Geography
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Q:

Why ABC computer is called so ?

A) Because it was thought to be the first computer so named with first alphabets of English B) Because it was developed by Atanasoff and Berry
C) Both of above are the reason to name the computer ABC D) None of the above
 
Answer & Explanation Answer: A) Because it was thought to be the first computer so named with first alphabets of English

Explanation:
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Filed Under: Computer
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11 11448
Q:

Main storage is also called

A) Memory B) Control unit
C) Accumulator D) Register unit
 
Answer & Explanation Answer: A) Memory

Explanation:

In a computer, the area where the data is stored for the quick access by the computer's processor is called Main storage or Primary storage or Memory or RAM.

 

Hence, main storage is also called Memory.

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