Latest TCS Aptitude Question SOLUTION: if the average of terms of the given series 148,146,144,142,140.....is 125,then find the total number of tems in series

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if the average of terms of the given series 148,146,144,142,140.....is 125,then find the total number of tems in series

Asked In TCS vinaya (12 years ago)

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Garima  (12 years ago)

24 terms

Average of terms = (a+l)/2
125= (148+l)/2
l=102
also
l= a+(n-1)*d
here a=148,l=102,d=-2
hence
solving we get
n= 24

Is this solution Helpfull? Yes (29) | No (2)  

Rakesh Kumar  (12 years ago)

Let, there be n terms.
sum of n terms=n/2(2a+(n-1)d). where, a= 1st term d=common difference
here,a=148 d=-2

now, sum of n terms=n/2(2*148+(n-1)*-2)
Average ={n/2(2*148+(n-1)*-2)}/n
According to question :
average=125
so, {n/2(2*148+(n-1)*-2)}/n =125
=>n=24.

Is this solution Helpfull? Yes (13) | No (1)  

sathyapriya  (12 years ago)

125= (148+146+144+142)/4
==> 145-125=20
we consider 4 terms so +4 = 20 +4 =24

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