Aptitude tricks

 

 

                                                                             Time and Work

1.     Work from Days:

If A can do a piece of work in n days, then A's 1 day's work =	1	.
	n

2.     Days from Work:

If A's 1 day's work =	1	,	then A can finish the work in n days.
	n

3.     Ratio:

If A is thrice as good a workman as B, then:

Ratio of work done by A and B = 3 : 1.

Ratio of times taken by A and B to finish a work = 1 : 3.

A work is assigned to 6 men and 12 women and they could complete it in 3 days. It was also observed that together they can do 7 times as much work a man and a woman can do. In how many days would 14 women have done the work? 

6M+12W=1/3 

(6M+12W)=7(M+W)

14W=?          => 14W= 14/126  =>1/9  =>  9 Days ans.

Simple Interest

Compound Interest

Ratio and Proportion

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'A' ki age 'B' se 12 yr jyada/older hai to: A=B+12 

'A' is 12 yr younger than 'B' : A=B-12 ,     so carefull

H.C.F ka jadu: greatest find krne me: 

here H.C.F. is 10

second largest trick:
   1. find absolute diffrence(nr,dr) for all => then its LCM 
    2. calculate for all using (nr/abs diff)*LCM 

iss trick se increasing/decreasing order bhi kr skte ho

above is also work for second smallest

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root ko fraction me change kr => dr ka LCM => fir multilply all power 

root ke andar root ho to :
1. count root=> then 2^(total root), see in img

jadu: calculate no of triangle

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jadu: calculate no of square

other counting fig youtube playlist

Boats And Streams

upstream: against stream 

upstream speed:U=|B-S| , dhara ke virudhh

downstream speed: D=|B+S| , dhara ke saath

Boat speed: B=(U+D)/2       

stream speed: S =(U-D)/2

upstream and downstream me alag alag time hoga

lekin distance to same hai n

isliye, s=ut  (physics wala)

      Ut1=Dt2

       (B-S) t1=(B+S) t2

jadu: check prime or not

jo bhi no diya ho , uske just baad perfect square

 find kro

ab js no ka yah square hai, uske sare prime

 factor nikalo

ydi given no kisi factor se nhi kta to prime

e.g.

given no : 547

take perfect sq=576=> sq of 24 =>2*2*2*3=>2,3

547 nhi ktega 2 se

547 nhi ktega 3 se

isliye 547 is prime

                            unit digit concept

            total no of prime factor in expression

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What is the mean proportional (MP) between the MPs of (2/7 & 32/343) and (2 & 1/5000)?

A. 3/35

B. 4/35

C. 2/35

D. 2/175

Answer: Option C

Explanation:

Let the MP of 2/7 and 32/343 be x

x = √(2/7)*(32/343)

= √(64/4901)

= (8/49)

Let the MP of 2 and 1/5000 be y

y = √(2)*(1/5000)

= √1/2500

= 1/50

MP of x and y = √(8/49)*(1/50)

= √8/2450

= √4/1225

= 2/35

What is the mean deviation of the data: 8, 9, 12, 15, 16, 20, 24, 30, 32, 34?

A. 8

B. 10.2

C. 0

D. 9.2

Answer: Option A

Explanation:

Mean deviation = Sum of deviations from mean / Total observations

Mean = (8 + 9 + 12 + 15 + 16 + 20 + 24 + 30 + 32 + 34) /10

= 20

Mean deviation = (12 + 11 + 8 + 5 + 4 + 0 + 4 + 10 + 12 + 14) / 10

= 80/10

= 8

A sum invested on simple interest grows to Rs 22500 and Rs 25500 in seven and nine years respectively. What is the rate percentage of the interest?

A. 7.5

B. 9.6

C. 13.5

D. 12.5

Answer: Option D

Explanation:

Amount for 7 years = Rs. 22500    (mishradhan) => principal+interest

Amount for 9 years = Rs. 25500    (mishradhan) => principal+interest

Hence,

SI for 2 years = 25500 - 22500

= 3000

So, SI for 1 year = 3000/2

= Rs. 1500

SI for 7 years = 1500 * 7

= 10500

Principal = 22500 - 10500

= 12000

Simple Interest = PTR / 100

1500 = (12000*1*R) / 100

R = (1500*100)/12000

R = 12.5%

Mixture and allegation:

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