18
11 Two right angles are formed during each hourly period 4-5, 5-6, 6-7, 7-8, 8-9. However, when the clock reaches 9pm, this coincides with the second 90° between the hours of 8-9. The clock has then to reach approximately 9.34pm for the only occasion when the hands will be at 90° in the hour 9-10.
It can be 7:10am or 7:10pm on a 12 hour clock.
I'll go out on a limb here, make a possibly unwarranted assumption, rush in with no concern for my personal welfare to a place where angels fear to tread, and presume that you're talking about the angle formed by the hour- and minute hands of an old fashioned clock. On that assumption, I count eleven (11) of them.
22:10 on 24-hour clock 50 minutes before 11pm
9
9.5
14 hours
Six.
16 = 6 + 10 as 6am to 12 is 6 hours 12 to 10pm is 10 hours On a 24 hour clock 10pm is 22:00 hours so 22 - 6 = 16 also
109 hours
Id say between 8-10pm