# Clock Problems for CAT Exam Preparation

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Problems related to clocks are not that frequent in CAT Exam but are useful for other exams like XAT, SNAP, NMAT, etc. This post explains some basic concepts which would help in solving clock related problems. There are mainly 2 types of Clock related problems –

#### 1) Angle Related Problems :

Few things to always remember while solving angle related problems –

• Speed of the hour hand = 0.5 degrees per minute (dpm) {The hour hand completes a full circle or 360 degrees in 12 hours or 720 minutes}
• Speed of the minute hand = 6 dpm {The minute hand completes a full circle in 60 minutes}

#### A Simple Trick :

Many students find it difficult to picture the angle between the hands of the clock. However, a simple trick to solve this question can be to treat this as a problem of 2 racers running on a circular track. Angle can be treated as the distance covered and we can also use the concept of relative speed.

Here’s a solved example for you to better understand the trick –

#### 2) Problems based on In-correct clocks :

This happens in the case when a clock is running faster or slower than the expected pace. While solving these questions one should always choose the correct clock as the frame of reference.

#### Example :

A watch gains 5 seconds in 3 minutes and was set right at 9 AM. If it shows 4:15 in the afternoon on the same day, what is the correct time?

Ans: The watch gains 5 seconds in 3 minutes => 1 minute in 36 minutes From 9 AM to 4:15, the incorrect watch has moved 7 hours and 15 minutes = 435 minutes.
Also, when the incorrect watch moves for 37 minutes, the correct watch moves for 36 minutes.
Therefore, When the incorrect watch moves for 435 minutes, correct watch moves for (36/37)*435 = 7.05 hours (approx) = 423 minutes (approx)
7.05 hours from 9 AM is 4:03 PM.
The correct time is 4:03 PM.

Here is another solved example :