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If k is a positive integer, and if the units’ digit of k 2 is 4 and th
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10 Sep 2021, 09:42
10 Sep 2021, 09:42
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87% (00:41) correct
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If k is a positive integer, and if the units’ digit of \(k^2\) is 4 and the units’ digit of \((k + 1)^2\) is 1, what is the units’ digit of \((k + 2)^2\) ?
(A) 0
(B) 2
(C) 4
(D) 6
(E) 8
(A) 0
(B) 2
(C) 4
(D) 6
(E) 8
Retired Moderator
Joined: 19 Nov 2020
Posts: 326
Given Kudos: 64
GRE 1: Q160 V152
If k is a positive integer, and if the units’ digit of k 2 is 4 and th
[#permalink]
10 Sep 2021, 10:20
10 Sep 2021, 10:20
1
edited/misreading the question 
Out all unit digits only 2 and 8 will square to the unit's digit equal to 4.
When \((k+1)^2\) has unit's digit 1, this will imply k has unit's digit added by 1. Out of (2+1) and (8+1) choices, only 8 will be the right choice. The unit's digit of \((k + 2)^2\) is 0, as \((8+2)^2=100\) Answer is A
Out all unit digits only 2 and 8 will square to the unit's digit equal to 4.
When \((k+1)^2\) has unit's digit 1, this will imply k has unit's digit added by 1. Out of (2+1) and (8+1) choices, only 8 will be the right choice. The unit's digit of \((k + 2)^2\) is 0, as \((8+2)^2=100\) Answer is A
Carcass wrote:
If k is a positive integer, and if the units’ digit of \(k^2\) is 4 and the units’ digit of \((k + 1)^2\) is 1, what is the units’ digit of \((k + 2)^2\) ?
(A) 0
(B) 2
(C) 4
(D) 6
(E) 8
(A) 0
(B) 2
(C) 4
(D) 6
(E) 8
gmatclubot
If k is a positive integer, and if the units’ digit of k 2 is 4 and th [#permalink]
10 Sep 2021, 10:20
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