"Question Banks" #25, Fractions, Decimals and Percents

[walter.hoffman]

Hi-

Can you please help me with one of the problems from the question banks.

Why can’t the answer to this question be 3? If the number is 10 and 10 squared is 100 and 10 cubed is 1,000. So the units digits of p cubed minus p squared is 0....so p+3 would be 3?

Thanks,

Walter

Given that p is a positive even integer with a positive units digit, if the units digit of p3 minus the units digit of p2 is equal to 0, what is the units digit of p + 3?
Top of Form



3


6


7


9


It cannot be determined from the given information.

[tim]

The units digit of 10 is 0 - not a positive integer.

[MarthaM266]

[size=100][/size]

One follow-up question, how did you determine from the beginning that this wasn't a double digit number?

Thanks!

[RonPurewal]

it could have two digits.
or it could have three digits.
or it could have five thousand million digits.

nothing in the problem is concerned with anything other than the UNITS digit (the 'ones place'—the digit farthest to the right). so any digits to the left are irrelevant.