can any one explain me the solution for this?? its from progressions chapter:
one side of a staircase is to be closed in by a rectangular planks from the floor to each step. the width of each plank is 9 inches and their height are successively 6,12,18 inches and so on.. there are 24 planks required in total. find the area in square feet.
pls expalin me the solution.
Ok so you can find the area of each rectangular plank, hts are 6,12,18..24 terms, but since area =l*width and the width is a constant it's easier to find the summation of the lengths and then multiply with the width summation(6,12,18..24 terms) is na + /2 that gives you 75 * 24inches or 150 feet area will be 150 * (9/12)feet or 112.5 sq feet
thanks vivek... lemme tell u wat i tried actually.. if possible expalin wats wrong in that.. i used the same AP formula.. but did the entire pbm without converting to feet. after finding the area in inches i converted to feet but the ans was not matching.. anything wrong in doing so?
thanks vivek... lemme tell u wat i tried actually.. if possible expalin wats wrong in that.. i used the same AP formula.. but did the entire pbm without converting to feet. after finding the area in inches i converted to feet but the ans was not matching.. anything wrong in doing so?
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I think, for converting, rather than multiplying the answer with 1/144 u were multiplying it with 1/12 ( since the answer is in square inches (1/12)^2 should be multiplied). Even i did the same for the first time 😛
hey yeah.. u wer exactly ryt.. but shudn multiply by 81/144.. shud multiply by 9/144....!!!! thanks a lot... i ve one more qn.. will post now.. wru by the way and wat u doing..
Ok so you can find the area of each rectangular plank, hts are 6,12,18..24 terms, but since area =l*width and the width is a constant it's easier to find the summation of the lengths and then multiply with the width summation(6,12,18..24 terms) is na + /2 that gives you 75 * 24inches or 150 feet area will be 150 * (9/12)feet or 112.5 sq feet
hey thanks.. ve got one more doubt.. solve for me if possible.. qn goes like this.. its all from arun sharma...
sum of three terms of a GP is 14 and the sum of their squares is 84. wat is the biggest term of the series??
so the sum a/r + a + ar=14 => r+1/r = 14/a - 1 ------------------
now sum of the squares (a/r)^2 + a^2 + (ar)^2= 84 =>r^2+(1/r)^2= 84/a^2 - 1----------------------
now (a+b)^2= a^2 + b^2 +2ab so a^2+b^2 = (a+b)^2 - 2ab
applying this formula to we get (r+1/r)^2 -2=84/a^2 -1
from (14/a -1)^2 - 2 =84/a^2 -1
now expand and solve the equation u will get a=4 and r=2 or 1/2
a/r=2 or 8 a=4 ar=8 or 2
so the answer is 8
btw My name is vivek sinha and i am a software engineer in cognizant kolkata.
wow.. thats really cool.. was dying how to solve after getting he eqns.. btw am karthik working in LNT ryt now staying in vizag.. nice to meet you.. thank you so much for ur answers..
soln 33 We need to find the general term of the series.
On analysis of the series u will find, it can be written as 2/(n(n+1)) = 2
so the series can be rewritten as 2
so finally the sum will be 2 ----------------------------------------
here n=infinity so n+1 also = infinity
and 1/infinity ->0
so the answer will be 2
soln 35 the series can be rewritten as 1/2 which is same as the above series so the general term will be 1/n*(n+1)
the last term of the series is 1/182 so 1/n(n+1)=1/182
on solving n=13
from the sum of the series would be 1/2 * 2 =1-1/(n+1)
put n=13
=13/14
Thx for d solution mate I was desperately w8ing for the solution jus one more doubt which I feel for me is that how to approach to general term like there are not many questions to approach to general term in Arun sharma so I take lot of time approaching general term by hit n trial..
Two requests: 1.How to approach to general term after seeing the series 2.Source for some more questions like dat?
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Reply for the query ............oly I dint mean that jus was restless.........No personal comments plzz u shld refrain from ur do's which u r doin and plzz don waste my tyme if u have answers plz pour dem else kindly stay away
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