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Number Properties + Average!!

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Number Properties + Average!!

by apoorva.srivastva » Fri Feb 19, 2010 11:23 am
The Values of five numbers are either 10,20 or 30. What is the average of 5 numbers?

1.) 4 numbers are less than 30
2.) 2 numbers are greater than or equal to 20

please explain the reasoning!!

OA is C
Last edited by apoorva.srivastva on Fri Feb 19, 2010 11:59 am, edited 1 time in total.
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by harsh.champ » Fri Feb 19, 2010 11:39 am
apoorva.srivastva wrote:The Values of five numbers are 10,20 or 30 repectively. What is the average of 5 numbers?

1.) 4 numbers are less than 30
2.) 2 numbers are greater than or equal to 20

please explain the reasoning!!

OA is C
Shouldnt it be values of three no.s are 10,20 and 30 rather than for 5 no.s
Also,it is written respectively but or is also written.
Is the question correctly written??
Can u plz check??
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by apoorva.srivastva » Fri Feb 19, 2010 12:00 pm
harsh.champ wrote:
apoorva.srivastva wrote:The Values of five numbers are 10,20 or 30 repectively. What is the average of 5 numbers?

1.) 4 numbers are less than 30
2.) 2 numbers are greater than or equal to 20

please explain the reasoning!!

OA is C
Shouldnt it be values of three no.s are 10,20 and 30 rather than for 5 no.s
Also,it is written respectively but or is also written.
Is the question correctly written??
Can u plz check??
I have edited the post ...but the question stem says 5 nos and not 3 nos!!
this is a bit tricly DS qustion
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by harsh.champ » Fri Feb 19, 2010 12:10 pm
apoorva.srivastva wrote:The Values of five numbers are either 10,20 or 30. What is the average of 5 numbers?

1.) 4 numbers are less than 30
2.) 2 numbers are greater than or equal to 20

please explain the reasoning!!

OA is C
Okay,now its fine.
1:- 4 numbers are less than 30.
Hence,the 5th no. is 30.
But we dont know the values of the other 4 numbers.Hence insufficient.

2:-2 numbers are GT or ET 20 .Still,it is insufficient.

Taking both 1 & 2 together ,
4 numbers are less than 30.[Frm 1]
Hence,the 5th no. is 30.
Now,2 no.s are greater than or equal to 20 .[Frm 2]
So, from 1 and 2 we get that the 4th no. is 20.

So,we can deduce that the rest of the 3 no.s are 10.

Hence,average = (3 x 10 + 20 + 30)/5 = 80/5
Hence,C.

I hope the explanation is clear.
It takes time and effort to explain, so if my comment helped you please press Thanks button :)



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by apoorva.srivastva » Fri Feb 19, 2010 12:23 pm
yeh mate ur explanation is cool....your approach and my approach is the same!!

but i took around 5 mints to crack it :(

was trying to look for an alternate approach!! i guess this is the best way to approach it :)
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by shashank.ism » Sun Feb 21, 2010 6:14 am
apoorva.srivastva wrote:The Values of five numbers are either 10,20 or 30. What is the average of 5 numbers?

1.) 4 numbers are less than 30
2.) 2 numbers are greater than or equal to 20

please explain the reasoning!!

OA is C
Values of five numbers are either 10,20 or 30... so 2 numbers or more are equal..
St.1) 4 nos. are less than 30 hence one no. is 30 and other numbers could be (10,10,10,10),(20,20,20,20),(10,20,20,20)==========not suff..
St.2) 2 numbers are greater than or equal to 20. so so numbers may be (20 ,20), (30,30), (20,30)==========not suff..
Combined:
numbers are 20,30,10,10,10
av. of numbers = (20+30+10+10+10)/5 = 16 suff...Ans C
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