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Question

By looking in a mirror, it appears that it is 6:30 in the clock. What is the real time?

The correct answer is

(a) 5:30

Understanding Mirror Reflection of Clock Time

When you look at a clock in a mirror, you see a reflection. A mirror causes lateral inversion, which means the image is flipped horizontally. The left side of the object appears on the right side in the mirror, and the right side appears on the left.

For a clock face, this means the numbers and hands appear reversed. For example, if the hour hand is pointing towards 3, in the mirror it will look like it's pointing towards 9. Similarly, if it's pointing towards 2, it will look like it's pointing towards 10.

Method to Calculate Real Time from Mirror Time

A common and simple trick to find the real time when you know the mirror time (or vice versa) is to subtract the given time from 12:00. Since we work with hours and minutes, it's often easier to think of 12:00 as 11:60 (11 hours and 60 minutes).

The formula is:

\(\text{Real Time} = 12:00 - \text{Mirror Time}\)

or

\(\text{Real Time} = 11:60 - \text{Mirror Time}\)

Step-by-Step Calculation

The question states that the time seen in the mirror is 6:30.

We need to find the real time.

  1. Identify the mirror time: 6:30.
  2. Use the formula: Real Time = 11:60 - Mirror Time.
  3. Substitute the mirror time into the formula: Real Time = 11:60 - 6:30.
  4. Subtract the minutes: 60 minutes - 30 minutes = 30 minutes.
  5. Subtract the hours: 11 hours - 6 hours = 5 hours.
  6. Combine the hours and minutes: 5 hours and 30 minutes.

So, the real time is 5:30.

Verifying the Options

Let's check the options provided:

  • (a) 5:30: This matches our calculation.
  • (b) 6:00: Subtracting from 11:60 gives 11:60 - 6:00 = 5:60 or 6:00. So, 6:00 in the mirror is 6:00 real time (or vice versa, 12:00 corresponds to 12:00 or 11:60 - 12:00 which isn't standard arithmetic, but 12 is the center point). 6:00 is not the mirror image of 6:30.
  • (c) 4:30: The mirror image of 4:30 would be 11:60 - 4:30 = 7:30. So, 4:30 is not the real time.
  • (d) 6:30: If the real time was 6:30, the mirror time would be 11:60 - 6:30 = 5:30. So, 6:30 is not the real time.

Based on our calculation and option verification, the real time is 5:30.

Revision Table: Mirror Time vs. Real Time Examples

Real Time Calculation (11:60 - Real Time) Mirror Time
1:00 11:60 - 1:00 = 10:60 11:00
3:00 11:60 - 3:00 = 8:60 9:00
6:00 11:60 - 6:00 = 5:60 6:00
8:00 11:60 - 8:00 = 3:60 4:00
10:00 11:60 - 10:00 = 1:60 2:00
5:30 11:60 - 5:30 = 6:30 6:30

Additional Information on Clock Mirror Images

The method of subtracting from 12:00 (or 11:60) works because 12:00 acts as the line of reflection on a clock face. If you fold the clock face in half vertically along the 12 and 6, symmetric times add up to 12:00 (e.g., 1 and 11, 2 and 10, 3 and 9, etc.).

This method applies to both finding the real time from the mirror time and finding the mirror time from the real time.

For times involving seconds, you would subtract from 11:59:60.

Consider the hours 12 and 6. The number 12 remains visually similar in a mirror (though inverted), and 6 flips to look somewhat like a 9. The position of the hands at 12 and 6 are on the vertical axis, which is the line of symmetry for the reflection, so hands pointing exactly at 12 or 6 will still appear to point at 12 or 6, respectively.

For 6:30, the minute hand is pointing directly at 6. In the mirror, it will still appear to point at 6. The hour hand is halfway between 6 and 7. In the mirror, it will be halfway between 5 and 6, but on the opposite side of the 6. The hour hand will appear to be halfway between 5 and 6, pointing towards 5.

This visual analysis confirms the mathematical calculation: the time that appears as 6:30 in the mirror is actually 5:30.

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Important Questions from Time and Work

  1. A man, a woman, and a boy can do a work in 6, 9, and 18 days respectively. How many boys must assist one man and one woman to do the work in 1 day?

  2. A, B, and C worked together for 5 days to build a wall and then B left the work. A and C together finished the remaining work in 5 days. In how many days can A and C working together finish building the whole wall if B alone can do it in 25 days?

  3. Three men can complete a work in 6 days and five women can complete the same work in 18 days. In how many days can 4 men and 10 women together complete the same work?

  4. Mother, daughter, and son can do a work in 3, 4, and 5 days respectively. How many days will they take to complete the work, if they work together?

  5. Rajan does 7/11 of a work in 21 days. How many more days will he take to complete the work?

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