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If light switches numbered from 1 to 4 are either on or off in differe
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16 Apr 2022, 07:24
16 Apr 2022, 07:24
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71% (01:34) correct
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If light switches numbered from 1 to 4 are either on or off in different combina-tions and switches 1 and 2 are always opposite (e.g., when switch 1 is on, switch 2 is oft), how many different combinations are there if at least one light is on?
(A) 7
(B) 8
(C) 15
(D) 16
(E) 27
(A) 7
(B) 8
(C) 15
(D) 16
(E) 27
Part of the project: Skill Builder Project for a Q170
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GRE Math Essentials for a TOP Quant Score - Q170!!! (2021)
GRE Geometry Formulas for a Q170
GRE - Math Book
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GRE Math Essentials for a TOP Quant Score - Q170!!! (2021)
GRE Geometry Formulas for a Q170
GRE - Math Book
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Re: If light switches numbered from 1 to 4 are either on or off in differe
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29 Apr 2022, 02:39
29 Apr 2022, 02:39
Carcass wrote:
If light switches numbered from 1 to 4 are either on or off in different combina-tions and switches 1 and 2 are always opposite (e.g., when switch 1 is on, switch 2 is oft), how many different combinations are there if at least one light is on?
(A) 7
(B) 8
(C) 15
(D) 16
(E) 27
(A) 7
(B) 8
(C) 15
(D) 16
(E) 27
Part of the project: Skill Builder Project for a Q170
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GRE Math Essentials for a TOP Quant Score - Q170!!! (2021)
GRE Geometry Formulas for a Q170
GRE - Math Book
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GRE Math Essentials for a TOP Quant Score - Q170!!! (2021)
GRE Geometry Formulas for a Q170
GRE - Math Book
Case I:
1 is ON and 2 is OFF - we can have 2 options for 3 and 2 options for 4.
i.e. (2)(2) = 4 options
Case II:
1 is OFF and 2 in ON - again, we can have 2 options for 3 and 2 options for 4.
i.e. (2)(2) = 4 options
Total combinations = 4 + 4 = 8
Hence, option B
gmatclubot
Re: If light switches numbered from 1 to 4 are either on or off in differe [#permalink]
29 Apr 2022, 02:39
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