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Suppose n is a two-digit positive integer with units digit 5
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09 Sep 2018, 19:44
09 Sep 2018, 19:44
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Question Stats:
67% (01:34) correct
32% (02:16) wrong based on 31 sessions
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Suppose \(n\) is a two-digit positive integer with units digit 5, and tens digit u. Now, if \(E=\frac{(n^2-25)}{100}\), then express E in terms of u.
A. \(u+1\)
B. \(u^2+1\)
C. \(u^2-u\)
D. \(u^2+u\)
E. \(u^2+u+1\)
Here is how I did it:
E
=(n^2-25)/100
=[(n+5)(n-5)]/100
=[(u+1)*10*(u-1)*10]/100
=(u+1)(u-1)
=u^2-1, which is not an choice so I don't know where I did wrong.
A. \(u+1\)
B. \(u^2+1\)
C. \(u^2-u\)
D. \(u^2+u\)
E. \(u^2+u+1\)
Here is how I did it:
E
=(n^2-25)/100
=[(n+5)(n-5)]/100
=[(u+1)*10*(u-1)*10]/100
=(u+1)(u-1)
=u^2-1, which is not an choice so I don't know where I did wrong.
Re: Suppose n is a two-digit positive integer with units digit 5
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10 Sep 2018, 10:50
10 Sep 2018, 10:50
5
from the question, it can be said that n=10u+5.
now just plug it into the expression for E and then you'll get u^2+u after a little calculation.
answer D
now just plug it into the expression for E and then you'll get u^2+u after a little calculation.
answer D
General Discussion
Re: Suppose n is a two-digit positive integer with units digit 5
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10 Nov 2018, 07:25
10 Nov 2018, 07:25
answer must be D only
n = 10u+5
n = 10u+5
