Quantitative Aptitude - Arithmetic Ability Questions

Q:

On multiplying a number by 7, the product is a number each of whose digits is 3. The smallest such number is  ?

A) 476190476 B) 48617
C) 47619 D) 4587962
 
Answer & Explanation Answer: C) 47619

Explanation:

By hit and trail, we find that

47619 x 7 = 333333.

7) 333333 (47619
    333333
----------------
        0

And 476190476 x 7 = 3333333333 but smallest number is 47619.

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Filed Under: Problems on Numbers
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16 14448
Q:

Time taken by P alone to finish a work is 50% more than the time taken by P and Q together. Q is thrice as efficient as R. If Q and R together can complete the work in 22.5 days, then how many days will P alone take to complete the work ?

A) 17 days B) 11 days
C) 15 days D) 16 days
 
Answer & Explanation Answer: C) 15 days

Explanation:

We know that Time is inversely proportional to Efficiency

Here given time ratio of P & P+Q as

P/P+Q = 150/100 = 3:2

Efficiency ratio of P & Q as

P:Q = 2:1 ....(1)

Given Efficiency ratio of Q & R as

Q:R = 3:1 ....(2)

From (1) & (2), we get

P:Q:R = 6:3:1

P alone can finish the work in

22.5(3+1)/6 = 15 days.

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Filed Under: Time and Work
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18 14445
Q:

A man covers a distance of 1200 km in 70 days resting 9 hours a day, if he rests 10 hours a day and walks with speed 1½ times of the previous in how many days will he cover 840 km ?

A) 39 days B) 37 days
C) 35 days D) 33 days
 
Answer & Explanation Answer: C) 35 days

Explanation:

Distance d = 1200km
let S be the speed

he walks 15 hours a day(i.e 24 - 9)
so totally he walks for 70 x 15 = 1050hrs.

S = 1200/1050 => 120/105 = 24/21 => 8/7kmph


given 1 1/2 of previous speed
so 3/2 * 8/7= 24/14 = 12/7

New speed = 12/7kmph

Now he rests 10 hrs a day that means he walks 14 hrs a day.

time = 840 x 7 /12 => 490 hrs
=> 490/14 = 35 days

So he will take 35 days to cover 840 km.

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Filed Under: Time and Distance
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20 14440
Q:

Two trains are moving in the same direction at 72 kmph and 36 kmph. The faster train crosses a girl sitting at window seat in the slower train in 32 seconds. Find the length of the faster train ?

A) 170 m B) 100 m
C) 270 m D) 320 m
 
Answer & Explanation Answer: D) 320 m

Explanation:

Relative speed = (72 - 36) x 5/18 = 2 x 5 = 10 mps.
Distance covered in 32 sec = 32 x 10 = 320 m.

The length of the faster train = 320 m.

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Filed Under: Problems on Trains
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11 14437
Q:

A man is 24 years older than his son. In two years, his age will be twice the age of his son. The present age of his son is

A) 20 B) 21
C) 22 D) 23
 
Answer & Explanation Answer: C) 22

Explanation:

Let the son's present age be x years. Then, man's present age = (x + 24) years
=> (x + 24) + 2 = 2(x + 2)
=> x + 26 = 2x + 4
So, x = 22

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43 14424
Q:

There are four prime numbers written in ascending order of magnitude. The product of the first three is 385 and of the last three is 1001. Find the fourth number ?

A) 17 B) 19
C) 13 D) 11
 
Answer & Explanation Answer: C) 13

Explanation:

(385/1001) = 5/13

First Number is 5

=> Fourth number is 13 

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Filed Under: Problems on Numbers
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14 14387
Q:

A sector of 120 degrees, cut out from a circle, has an area of 66/7 sq cm. Find the radius of the circle.

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

Explanation:

πr=667

 r =3

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Filed Under: Area
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13 14385
Q:

A shopkeeper sold a mobile phone for Rs. 12000. Had he offered discount of 10% on the selling price, there would be a loss of 4%. What is the cost price of that Mobile phone?

A) Rs. 12,500 B) Rs. 11,250
C) Rs. 12,750 D) Rs. 11,680
 
Answer & Explanation Answer: B) Rs. 11,250

Explanation:

Given that SP = Rs. 12000 - 10%  = Rs. 10,800

Loss% = 4

We know that, C.P = 100/(100 - Loss%) x 100

=> 100/100-4 x 10800

=> 1080000/96

C.P = Rs. 11,250

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Filed Under: Profit and Loss
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14 14362