cats and dogs

on Monday, a certain animal shelter housed 55 cats and dogs. by Friday, exactly 1/5 of the cats and 1/4 of the dogs had been adopted; no new cats and dogs were brought to the shelter during this period. What is the greatest possible number of pets that could have been adopted from the animal shelter...

positive integers - mulitple

if a and b are positive integers, is a a multiple of b?
1, every prime factor of b is also a prime factor of a.
2, every factor of b is also a factor of a.

Great thanks.

Integers

If P is a set of integers and 3 is in P, is every positive multiple of 3 in P?
1, for any integer in P, the sum of 3 and that integer is also in P.
2. for any integer in P, that integer minus 3 is also in P.

thanks.

Units degit

x, y, z are consecutive positive integers such that x< y< z. If the units digit of x2 is 6 and the units of y2 is 9, what is the units digit of z2?
A. 0
B. 1
C. 2
D. 4
E. 5

Pls help me. Million thanks.

what is the units digit????

Mayonnai5e, thank you for your useful post. I know which books I should befriend now.

Hello AleksandrM, It is A. In order to know which set has the greatest standard deviation, we must find out the standard deviation of each set as Netigen did. A. {-3, 1, 2} mean =0 ---> 14/3 B. {-2, -1, 1, 2} mean=0 --> 10/4 C. {3, 5, 7}mean=5 ---> 8/3 D. {-1, 2, 3, 4}mean=2 ---> 14/4 E. {0, 2, 4} m...

Standard Deviation

which of the following distribution of numbers has the greatest standard deviation?
A. {-3, 1, 2}
B. {-2, -1, 1, 2}
C. {3, 5, 7}
D. {-1, 2, 3, 4}
E. {0, 2, 4}

Pls show me some strategies to do standard deviation since I am usually scared of it. Thanks