Q9 of 45 Page 164

What is the angle between the hour’s hand and minute’s hand of a clock at (i) 1.40 hours, (ii) 2.15 hours? (Use 1° = 60 minutes.)

Hour’s hand rotates 360° in = 12 hour = 720 min


Minute’s hand rotates 360° in = 1 hour = 60 min


i) At, 1.40hrs


Time past after 0.00 hrs = 1 hr + 40 min = 100 min


In 100 min hour’s hand rotate =


In 100 min⁡minute’s hand rotate =


∴ Difference between the hands,


= 240° - 50°


= 190°


ii) At 2.15 hrs,


Time past after 0.00 hrs = 2 hr + 15 min = 135 min


In 135 min hour’s hand rotate =


In 135 min minute’s hand rotate =


∴ Difference between the hands,


= 90° - 67.5°


= 22.5°


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