Data Sufficiency

Pls explain..

The difference between Mary's and Jim's annual salaries was twice the difference between Mary's and Kate's salaries.If Mary's annual salaries was the highest of the three,then what was the average annual salary of the three people?

(1)Jim's annual salary was $30000 that year
(2)Kate's annual salary was $40000 that year




In the XY plane,at what two points does the graph of y=(x+a)(x+b) intersect the x-axis?
(1)a+b=-1
(2)The graph intersects the y-axis at (0,-6)


Thanks

M-J = 2(M-K)

M,K and J are the salaries of Mike Jim and Kate respectively.

Question is asking for (M+J+K)/3

1. Gives only Jim's salary - Insufficient
2. Gives only Kate's salary - Insufficient

Using 1 and 2, we can get Mike's salary

Answer is C

I used the same method to solve the 1st question..But the answer is B not C..

moneyman wrote:Pls explain..

The difference between Mary's and Jim's annual salaries was twice the difference between Mary's and Kate's salaries.If Mary's annual salaries was the highest of the three,then what was the average annual salary of the three people?

(1)Jim's annual salary was $30000 that year
(2)Kate's annual salary was $40000 that year

m-j = 2(m-k)
m=2k-j

We are asked to find (m+j+k)/3
=(2k-j + j + k)/3
= k

1 - insufficient. We need to know m,j or k.

2 - sufficient. k alone is sufficient.

Hence B

moneyman wrote: In the XY plane,at what two points does the graph of y=(x+a)(x+b) intersect the x-axis?
(1)a+b=-1
(2)The graph intersects the y-axis at (0,-6)


Thanks

We need to find points a and b

1 - insufficient. We can't find a and b.
0 = x^2 -x + ab

2 - insufficient. ab = 6
0 = x^2 +(a+b)x -6

Using 1 and 2, you get

x^2 -x -6 = 0
x = 3, x = 2

Hence C