Find the time between 7 and 8 o'clock when two hands are at right angles?  Pick one.
A) 2 2/11 minutes past 7 o'clock
B) 3 2/11 minutes past 7 o'clock
C) 21 9/11 minutes past 7 o'clock
D) 7 10/11 minutes past 7 o'clock
E) 8 10/11 minutes past 7 o'clock
angle=90 deg   so,   angle=30(h)-11/2(min)   =&gt; 90=30(7)-11/2(min)   =&gt;210-90=11/2(min)   =&gt; (120*2)/11=min   =&gt; min=21 9/11 min   ANSWER:21 9/11 minutes past 7 o'clock
<result>C</result>
Find the time between 7 and 8 o'clock when two hands are at right angles?