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29 Mar 2019, 10:32
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E
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
45%
(medium)
Question Stats:
70% (01:56) correct
30%
(02:01)
wrong
based on 153
sessions
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Find an average of ages of eight students.
a) If you remove the youngest student, the average will increase by thirty-one years.
b) If you remove the oldest student, the average will decrease by twenty-five years.
a) If you remove the youngest student, the average will increase by thirty-one years.
b) If you remove the oldest student, the average will decrease by twenty-five years.
29 Mar 2019, 13:08
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Question: calculate average (\(Av\)) of sum of ages (\(S\)) of 8 students.
from statement 1: let youngest age be "\(a\)"
\(\frac{S - a}{8-1}\) = \(\frac{S}{8}\) + 31
\(8S-8a = 7S + (31*7*8)\)
\(S - 8a = (31*7*8)\)
\(\frac{S}{8} = Av = a + (31*7)\) --> we have two unknowns, so insufficient
from statement 2: let eldest age be "\(b\)"
\(\frac{S - b}{8-1}\) = \(\frac{S}{8}\) - 25
\(8S-8b = 7S - (25*7*8)\)
\(S - 8b = -(25*7*8)\)
\(\frac{S}{8} = Av = b - (25*7)\) --> we have two unknowns, so insufficient
by combining,
only an equation relating the difference between "\(a\)" and "\(b\)" can be formed: \(b - (25*7) = a + (31*7)\) , and \(b-a = (56*7)\)
while \(Av\) is still unknown
E
from statement 1: let youngest age be "\(a\)"
\(\frac{S - a}{8-1}\) = \(\frac{S}{8}\) + 31
\(8S-8a = 7S + (31*7*8)\)
\(S - 8a = (31*7*8)\)
\(\frac{S}{8} = Av = a + (31*7)\) --> we have two unknowns, so insufficient
from statement 2: let eldest age be "\(b\)"
\(\frac{S - b}{8-1}\) = \(\frac{S}{8}\) - 25
\(8S-8b = 7S - (25*7*8)\)
\(S - 8b = -(25*7*8)\)
\(\frac{S}{8} = Av = b - (25*7)\) --> we have two unknowns, so insufficient
by combining,
only an equation relating the difference between "\(a\)" and "\(b\)" can be formed: \(b - (25*7) = a + (31*7)\) , and \(b-a = (56*7)\)
while \(Av\) is still unknown
E
29 Mar 2019, 13:33
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Let the avg of 8 student is x, and the age of the youngest is a & the age of the oldest one is b.
i. 7(31+x)+a=8x ... 2 variable 1 eqn.... x can not be determined. ------NS
ii. 7(x-25)+b=8x ... 2 variable 1 eqn.... x can not be determined. ------NS
Hence Ans is E.
i. 7(31+x)+a=8x ... 2 variable 1 eqn.... x can not be determined. ------NS
ii. 7(x-25)+b=8x ... 2 variable 1 eqn.... x can not be determined. ------NS
Hence Ans is E.
