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dimitri92
What could be the range of a set consisting of odd multiples of 7?
a)21
b)24
c)35
d)62
e)70

I like the question.

The range of the set of multiples of 7 must be even multiple of 7. Which is only 70 among the answer choices.
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I am sorry... I may sound a bit stupid but still i dont understand. First of all i dont understand what does it mean by range and why range must be even multiple of 7?
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As I know range means : Largest no. - Smallest no. in a set.
And as per the question its asking what could be the range .

Odd multiples of 7 means 7 *(2k+1) ..so smallest in this set can me where k=0 i.e 7
and largest in this set can be 7*(2k+1) where k is some finite max number.
So Range = 7*(2k+1) - 7 = 14k . This range should be in the form of a multiple of 14 , and as per the options I can see only 70 is the multiple of 14 .

Answer E
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Thank you guys.... I really appreciate the job you are doing on this forum.. Keep it up...
Thanks Again for your great help...
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range= last number( which is odd number) -first number( which is odd number too)
in this case, range = odd number - odd number = even number.
this narrow the answer to b,d, e
from property of factor: a multiple of 7 - multiple of 7= multiple of 7
so 70 is the only multiple of 7 among b,d and e
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Here you go:

Range = the difference between the greatest and the smallest numbers in the sequence. Our sequence is odd and is a multiple of 7. Every number in that sequence can be represented like this: 7*(2n+1) where n is any positive integer.

Range = 7*(2m + 1) - 7*(2n + 1) = 7*2*(m-n) = 14 * (m-n).

m, n - any positive integers

The answer must be divisible by 14, which is only 70.

The correct answer is E.
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[quote="Fistail] I like the question.

The range of the set of multiples of 7 must be even multiple of 7. Which is only 70 among the answer choices.[/quote]

I was banging my head against the wall after reading the question. Thanks Fistail, never occured to me that it can be so easy to answer.
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you have taken 2n+1 as it says to find the odd no. range.....what if he says to find the even no. range then how should we move........
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dimitri92
What could be the range of a set consisting of odd multiples of 7?

A. 21
B. 24
C. 35
D. 62
E. 70

Well it has to be a multiple of 7 and since Odd - Odd = Even, then only E fits the bill

Hope it helps
Cheers!
J :)
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Bunuel
amitjash
I am sorry... I may sound a bit stupid but still i dont understand. First of all i dont understand what does it mean by range and why range must be even multiple of 7?

What could be the range of a set consisting of odd multiples of 7?
A. 21
B. 24
C. 35
D. 62
E. 70

The range of a set is the difference between the largest and smallest elements of a set.

Set consists of odd multiples of 7 (numbers of a type \(7*odd\)), so there can be following elements: ..., -7, 7, 21, 35, ...

The range of this set would be: \(7*odd_{max}-7*odd_{min}=7(odd_{max}-odd_{min})=7*even\), (as odd-odd=even). So the range is even multiple of 7.

Answer: E.

Hope it's clear.
Thank you!
I really like your post :thumbup:
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Here is my solution to this one-->

Range must be even and a multiple of 7.

Hence Range must be a multiple of 14.

Only Choice E is a multiple of 14

Hence E
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dimitri92
What could be the range of a set consisting of odd multiples of 7?

A. 21
B. 24
C. 35
D. 62
E. 70

Since the range of a set of numbers is defined as the difference between the largest number and the smallest number in the set, we can just calculate the difference between odd multiples of 7. For example, the difference between 21 and 7 is 14, between 35 and 7 is 28, between 77 and 21 is 56.

From the above examples, we see that the difference between two odd multiples of 7 must be an even multiple of 7 or, equivalently, a multiple of 14. Therefore, the correct answer is 70 since it is the only number in the answer choices that is a multiple of 14.

Answer: E
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