Quantitative Reasoning

Q1: A company has two type of machine R and S. Operating at constant rate, R does the job in 36 hr, s does the same job in 18 hr. If the company use the same number of each type of machine to do job in 2 hr, how many machine type r used?
a)2
b)4
c)6---->answer
d)10
e)12


Q2: If 2^x - 2^x-2= 3(12^13) what is the value of x?
a)9
b)11
c)13
d)15------->answer
e)17

Q3: For every positive even integer n, the function h(n) is defined to be the product of all even integers from 2 to n, inclusive. If P is the smallest prime factor of h(100)+1, then p is?

a)between 2 and 10
b)between 10 and 20
c)between 20 and 30
d)between 30 and 40
e)greater than 40--------> answer


Q4:If n is a positive integer and the product of all the integer from 1 to n inclusive is a multiple of 990, what is the least possible value for n?
a)10
b)11------>answer
c)12
d)13
e)15



Data sufficiency:
Q5: What is the tenth digit of positive integer r?

(1) the tens digit of r/10 is 3

(2)the hundred digit of 10r is 6


The answer is B (statement 2 alone sufficient) but i totally lost about that.


Q6:If x&y are positive integer, what value is xy?

(1)the greatest common factor x&y is 10

(2)the least common multiple of x& y is 180


the answer is C(Both statement is sufficient)----but i don't know how.





Thanks a lot