Question Bank - Logical Reasoning

Here's the question bank on all the logical reasoning topics.

Consider the following statements regarding clocks :(A) In 60 minutes, the minute hand gains 55 minutes on the hour hand (B) In every hour, both the hands coincide once (C) When the two hands are at right angles, they are 15 minutes spaces apart. Choose the correct statements from above :

A.
(A) and (C) only
B.
(A) and (B) only
C.
(B) and (C) only
D.
(A)

Solution:

Calculation:At 12:00 clock both hour and minute hands have an angle of 0 ° Then, minute angle for t minutes past 12\(\theta = {t \times {360 \over 60}} = 6 \times t\)Hour angle for t minutes past 12 \(\theta = { t \times {360 \over {12 \times 60}}} = {t \over 2}\)Statement A:For t = 60 minutesMinute hand moves\(6t = 360 ^\circ\)Hour hand moves\({t \over 2} = 30 ^\circ\)Overall difference in angle of both hands\(360 ^\circ - 30 ^\circ = 330 ^\circ\)For 330 ° the minute hands gap is \({330 \over 6} = 55\) minutesStatement B:At 12 both hands coincide. For the next coincide to happen the minute hand moves round the clock once and hour hand crosses 1 mark.\(6t = {360 + {t \over 2}} \\ {11 \over 2}t = 360 \\ t = {720 \over 11 }\\ t \approx 65 \)It takes about 65 minutes for the hands to coincide again - it takes more than an hour to get hands to coincideStatement CWhen 2 hands are 90° apart - an example at 3 o'clock it'll take t minutes for hands to overlap\(6t = { {3 \over 12} \times 360 + {t \over 2}} \\ 6t = { 90 + {t \over 2}} \\ {11 \over 2} t = 90 \\ t \approx 16\)It takes about 16 minutes for them to coincide. So they are 16 minutes apart.So, Statement A is correct.Hence, Option "4" is the correct answer.

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