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Q:

Application of Inverse Proportion

If 20 persons can do a piece of work in 7 days then calculate the number of persons require to complete the work in 28 days

Answer

Number of persons * days = work

20 * 7 = 140 man- days

Now, x * 28 = 140 men- days

=> x =5

Therefore in second case the required number of person is 5.

Second method:

Since work is constant, therefore M1 x D1= M2 x D2

20 x 7 = M2 x 28

=> M2 = 5

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Subject: Time and Work

Q:

A works twice as fast as B.If B can complete a work in 18 days independently,the number of days in which A and B can together finish the work is:

A) 4 days	B) 6 days
C) 8 days	D) 10 days

Answer & Explanation Answer: B) 6 days

Explanation:

Ratio of rates of working of A and B =2:1. So, ratio of times taken =1:2

Therefore, A's 1 day's work=1/9

B's 1 day's work=1/18

(A+B)'s 1 day's work= 1/9 + 1/18 = 1/6

so, A and B together can finish the work in 6 days

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Filed Under: Time and Work

Q:

A fort had provision of food for 150 men for 45 days. After 10 days, 25 men left the fort. The number of days for which the remaining food will last, is:

A) 29	B) 37
C) 42	D) 54

Answer & Explanation Answer: C) 42

Explanation:

After 10 days : 150 men had food for 35 days.

Suppose 125 men had food for x days.

Now, Less men, More days (Indirect Proportion)

$∴$ 125 : 150 :: 35 : x $\Leftrightarrow$ 125 x x = 150 x 35

$\Rightarrow x = \frac{150 \times 35}{125} = 42$

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Filed Under: Chain Rule

Q:

Some persons can do a piece of work in 12 days. Two times the number of such persons will do half of that work in

A) 6 days	B) 12 days
C) 4 days	D) 3 days

Answer & Explanation Answer: D) 3 days

Explanation:

Let x men can do the in 12 days and the required number of days be z

More men, Less days [Indirect Proportion]

Less work, Less days [Direct Proportion ]

$\begin{array}{r} \begin{matrix} m e n & 2 x & : & x \end{matrix} \\ \begin{matrix} w o r k & 1 & : & \frac{1}{2} \end{matrix} \end{array}\} : : 12 : z$

$∴ (2 x \times 1 \times z) = (x \times \frac{1}{2} \times 12)$

$\Rightarrow z = 3$

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Filed Under: Chain Rule

Q:

A boy multiplied 987 by a certain number and obtained 559981 as his answer. If in the answer both 98 are wrong and the other digits are correct, then the correct answer would be ?? please explain in detail

A) 553681	B) 555181
C) 555681	D) 556581

Answer & Explanation Answer: C) 555681

Explanation:

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Filed Under: Quantitative Aptitude - Arithmetic Ability
Exam Prep: Bank Exams

Q:

In an examination, a student scores 4 marks for every correct answer and loses I mark for every wrong answer. If he attempts in all 60 questions and secures 130 marks, the number of questions he attempts correctly, is:

A) 35	B) 38
C) 40	D) 42

Answer & Explanation Answer: B) 38

Explanation:

Let the number of correct answers be X.

Number of incorrect answers = (60 – X).

Therefore, 4x – (60 – x) = 130

=> 5x = 190 => x = 38

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Filed Under: Simplification

Q:

Insert the missing number.

3, 7, 6, 5, 9, 3, 12, 1, 15, (....)

A) 18	B) 13
C) -1	D) 3

Answer & Explanation Answer: C) -1

Explanation:

There are two series, beginning respectively with 3 and 7. In one 3 is added and in another 2 is subtracted.

The next number is 1 - 2 = -1.

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Filed Under: Odd Man Out

Q:

Insert the missing number.

2, 6, 12, 20, 30, 42, 56, (....)

A) 61	B) 64
C) 72	D) 70

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