Question

At what time between $7$ to $8$ $O$ clock the hands of the clock will be at right angle?

• A. $5\frac{5}{11}min$ and $38\frac{2}{11}min$ past $7$
• B. $55min$ and $20min$ past
• C. $55min$ and $10min$ past
• D. $\frac{600}{11}min$ and $\frac{900}{11}min$ part $7$`

Answer 1

The correct option is D $\frac{600}{11}min$ and $\frac{900}{11}min$ part $7$`

$Weknow$
$Ha-Hm=0.5(60\times H-11\times M)$
$given$
$Ha-Hm=90$
$H=7$
$plugginginthevalues$
$90=0.5(60\times 7-11\times M)$
$\Rightarrow M=21.8$
$Hence21minpast7thehandswillshowrightangle$