Given points r,s,t on the number line, is r+s has midpoint 0GHong14 wrote:
st(1) s is to the right of 0, but we don't know where is r. Not Sufficient
st(2) t-r=t-s OR r=-s; restate question -s + s has midpoint 0, we don't know where is s. Not Sufficient
Combining st(1&2) s is to the right of 0 and -s + s has midpoint 0 => symmetrical assumption. Sufficient
Answer C - Yes 0 is midpoint of r and s
