Latest Elitmus Aptitude Question SOLUTION: the average of 8 numbers is 20.the average of the first 2 numbers is 31/2 and that of the next 3 is 64/3.If the sixth be less than the seventh and eighth numbers by 4 and 7 respect

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(#M40163997) ELITMUS Numerical Ability question Keep an EYE

the average of 8 numbers is 20.the average of the first 2 numbers is 31/2 and that of the next 3 is 64/3.If the sixth be less than the seventh and eighth numbers by 4 and 7 respectively.then the 8th numbers is?

Asked In Elitmus Sniper (7 years ago)

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Jai Kumar  (5 years ago)

Total =20*8=160
Now total of first two numbers=31/2*2=31
Total of next 3 numbers=64/3*3=64
Total of first five number=64+31=95
Let sixth number be x
Than 7th number is x+4
8th number will x+7
Now (95+x+x+4+x+7)/8=20
106+3x=160
x=54/3=18
Therefore 8th no. will be x+7=18+7=25

Is this solution Helpfull? Yes (3) | No   

navin patel  (4 years ago)

let's eight number is a1,a2,a3,a4,a5,a6,a7,a8
given average of 8 number is = 20
so a1+a2+a3+a4+a5+a6+a7+a8=20*8=160...........(1)
then average of the first 2 number is = 31/2
so a1+a2=31
then next 3 is = 64/3
a3+a4+a5=64
then
a6=a7-4 and a6=a8-7
on solving above two equations,we find
a7=a8-3
on putting all value exept a8 in equations 1
then we find a8=25

Is this solution Helpfull? Yes (1) | No   

MANBODH KUMAR  (5 years ago)

Since avg of 8 number is 20.
Total sum = 8*20=160.
now it is given that avg of 1st and 2nd number is 31/2 and 3rd,4th,5th number is 64/3.
It means sum of number from 1 to 5 is 31+64=95.
now let 8th number be x , then 7th number be x-3 , and 6th number will be x-7 .
hence total sum = 95+(x-7)+(x-3)+(x)=160
it gives x=25.

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Mayank Tiwari  (3 years ago)

The sum of first five no will be = 31+64 = 95

Now to have an average of 20 , sum of 8 numbers will be = 160

Let sixth , seventh and eighth no be a , a+4 , a+7 respectively

Now

a + (a+4)+(a+7) = 160-95

So a= 18

So 8th no = (a+8) = 25

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