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niteshwaghray
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Bunuel
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sasidharrs
Bunuel, 40 = 2^3*5 and 50 = 2*5^2.
I agree that a is atleast 3.. but how is b EXACTLY 1.. I can do Z= 200, which is 2^3*5^2*7^0 .. so b can be 2 as well right..
am I missing something?

We are told that z is divisible by 5 but not by 5^2, so the power of 5 in z must be 1.
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BUNUEL: a can be equal to(not greater than 3) 3,4,5,6.... and b is equal to 1 to satisfy condition 1. hence, your solution is correct by chance. Hope this helps !!!
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BUNUEL: a can be equal to(not only greater than 3) 3,4,5,6.... and b is equal to 1 to satisfy condition 1. hence, your solution is correct by chance. Hope this helps !!!
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Hello!
If we consider Z = 280 then, 2^3 * 5^1 * 7^1 which means a-b =2
Therefore a-b can be greater or equal to 2 that is 9

Therefore shouldn't it be insufficient as no clear answer?

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Given Z=2^a×5^b×7^c

Task: Is 3^|a−b|<9? or we can rephrase the question as Is |a-b|=0 or Is |a-b|=1

(1) Z is divisible by 40 but not by 50
It gives the information that Z has factor as 2^3 x 5, and |a-b|>1. Sufficient

(2) Z^(a−b)=2^6×5^2×7^4
(2^a×5^b×7^c)^(a-b) = 2^6×5^2×7^4
2^a(a-b) x 5^b(a-b) x 7^c(a-b) = 2^6×5^2×7^4
a(a-b) = 6
b(a-b) = 2
Dividing above equations
a/b = 3
Therefore |a-b|>1. Sufficient

D is correct
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280 is disivible by 40 but not by 50. 40*7 =280

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niteshwaghray
\(Z=2^a×5^b×7^c\)

A positive integer Z can be expressed in terms of its prime factors as above, where a, b and c are positive integers. Is \(3^{|a−b|}<9\)?

(1) Z is divisible by 40 but not by 50
(2) \(Z^{a−b}=2^6×5^2×7^4\)

(1) If=3 and b=1 then Z will be divided by 40 but will not be divided by 50 and 3^2=9=9 not 3^2<9 Answer is NO. Sufficient.
(2) 6-2=8, 9^8 SUFFICIENT.
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