7. How many positive cubes less than 5000 end in the digit 5 ?
A 1
B 2
C 3
D 4
E 5
7. B For the cube of a positive integer to end in a 5, the integer itself must end in a 5 . We note that $5^{3}=125$ and that $15^{3}=3375$. However $25^{3}>20^{3}=8000$ and so $25^{3}>5000$.
Therefore there are only two positive cubes less than 5000 which end in the digit 5 , namely 125 and 3375 .