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Gurdeep Kaur

· started a discussion

· 1 Months ago

explanation (Question: 292681.0 )

can somebody please explain where this 720 came from?

Question:

A wall clock gains 2 minutes in 12 hours, while a table clock loses 2 minutes in 36 hours; both are set right at noon on Tuesday. What is the correct time when they both show the same time?

Options:
A)

11 : 45 am

B)

12 : 00 noon

C)

12 : 15 pm

D)

11 : 55 am

Solution:

Ans: (b)

In 36 hours, there would be gap of 8 minutes. The two watches would show the same time when gap would be exactly 720 min.

The number of 36 hrs time frames =  7208     = 90

∴Total time = 90 × 36 = 3240 hrs

Since 3240 is divisble by 24. So, watches would show correct time at 12 noon.

Shashank Shah

· commented

· 1 Months ago

Wall clock gains 2 min in 12 hrs or 6 min in 36 hours
table clock losses 2 min in 36 hrs

difference between 2 clocks in 36 hours 8 min

we need to find out when difference between both clock becomes 12 hours(as in standard clock after every 12 hours the time units shown by clocks are same)
difference between their times is 8min after 36 hours
so difference will be 12 hours after= 36*12*60/8 = 3240 hours

so they will show same time after 3240 hours means 3240/24=135 days

as we dont have extra hours or min,i.e., 3240 is exactly divisible by 24 so ans will be 12 noon
Suppose difference is 3244 hrs then 3244/24=135.16 i.e, 0.16*24=4 hours approx... 135 days and 4 hours , then the answer would have been 12:00 + 4 hrs =4:00 pm approx after 135 days
hope this may help you

VIJAY SINGH

· commented

· 1 Months ago

12 hour diffrence means both clock will show same time so 12hour=720min
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