gmat prep 2, number scale

[Woozler]

If m and r are two numbers on a number scale, what is the value of r?

(1) the distance between 0 and r is 3 times the distance between 0 and m
(2) 12 is halfway between m and r

what other choices are there except for 6 and 18?

[goyalsau]

If m and r are two numbers on a number scale, what is the value of r?

(1) the distance between 0 and r is 3 times the distance between 0 and m
(2) 12 is halfway between m and r

Value of r ?

(1) Let the Distance between 0 to r be r , Distance between 0 to m is m

r = 3m

Any value of r and m can be placed

In Sufficient

(2) 12 is halfway between m and r, { is the mean of m and r }

Try any values eg. 4 and 8 , (4+8)/2 = 6 , 6 is halfway between m and r

( m + r )/2 = 12 , m +r = 24 , it can be any value like 2 & 22, 3 & 21, 4 & 20 ,

Insufficient

Combining statements Together

m+r = 24 , r = 3m , 4m= 24 , m = 6, r = 18

Sufficient

It should be C,

[Geva@EconomistGMAT]

If m and r are two numbers on a number scale, what is the value of r?

(1) the distance between 0 and r is 3 times the distance between 0 and m
(2) 12 is halfway between m and r

what other choices are there except for 6 and 18?

Try m=-12 and r=36. 12 is the midpoint, and the 36 is 3 times 12.

there's a reason they said "numbers", not "positive numbers". Carefully note what the question says and doesn't say about variables: with a number line question, the issue is almost always positive Vs. negative numbers.

[gig92]

If m and r are two numbers on a number scale, what is the value of r?

(1) the distance between 0 and r is 3 times the distance between 0 and m
(2) 12 is halfway between m and r

what other choices are there except for 6 and 18?

Try m=-12 and r=36. 12 is the midpoint, and the 36 is 3 times 12.

there's a reason they said "numbers", not "positive numbers". Carefully note what the question says and doesn't say about variables: with a number line question, the issue is almost always positive Vs. negative numbers.

---
So it makes the ans: E

[Woozler]

Damn it, -12 and 36. How could I forget to consider the negative numbers. Thank you, Geva@MasterGMAT