duongthang wrote:Q1

in the sequence integer t1, t2,...tn, what is value of n

1, sum of the integer is 3124

2, mean of the integers is 72

Q2

in the sequence of positive number x1, x2, ...xn what is value of x1

1, xi=x(i-1) : 2 for example, x3=x2/2, x10=x9/2

2, x5=x4/x4+1

I do not understand what is sequence inhere. These questions is from GMATPREP software.

imo ans for bth is c

1st)
s1------->t1+t2+t3.....+tn=3124.....insuff

s2-------->(t1+t2+t3.....+tn)/n=72.....nothing else hence insuff

s1+s2---->3124/n=72-----> n can be found out
hence suff


2nd)
s1)------>Xi=X(i-1)------->insuff

s2) x5=x4/(x4+1)--------->insuff

combining
x5=x4/2--->x4/2=x4/(x4+1)------->x4=1
solving x1=8
seq=8,4,2,1
hence suff

duongthang wrote:Q1

in the sequence integer t1, t2,...tn, what is value of n

1, sum of the integer is 3124

2, mean of the integers is 72

Q2

in the sequence of positive number x1, x2, ...xn what is value of x1

1, xi=x(i-1) : 2 for example, x3=x2/2, x10=x9/2

2, x5=x4/x4+1

I do not understand what is sequence inhere. These questions is from GMATPREP software.

Post one question per thread please!

Your first question is invalid by itself, even if we go for [spoiler]C[/spoiler], how can the number of certain things contain fractional part to it?

Your second question is again leaving me in doubts, may be the brackets were not put where required while typing, if what I percieved is correct, then IMO [spoiler]C[/spoiler].

I faced this question yesterday.

AVERAGE=SUM OF TERMS/# OF TERMS

That should be all you need to know. Try practicing questions like "what is the sum of all even numbers between x and y..."