IMAT 2013 Q13 [Time Clock]

My watch is a twenty four hour digital watch, so that, for instance 4.17am appears as:


and 4.17pm appears as:


One morning recently I woke up, picked up my watch and saw:


I panicked, thinking that I had overslept, until I realised I had picked up the watch upside down and it was only one minute past five.

At which one of the following times would the display appear the same whichever way I picked it up?

A. 5.51am
B. 5.51pm
C. 1.01am
D. 3.21pm
E. 3.51pm

Simple steps to solve word problems:

  • Underline key information
  • Determine what they are trying to ask, and what you will need to solve it
    • Eliminate any non-essential information
  • Draw a picture, graph, or equation
    • In moments of high stress like exam taking, always work with the paper they give you to avoid careless mistakes.
  • Solve.

For this question, it is best solved with paper in hand, because you can rotate the paper upside down and hopefully solve the problem. First, check the examples given, understand what changes when you flip it upside-down and figure out which numbers can still be read upside-down (for example, 7 does not work when flipped but 5 and 1 do). Next, write out all the options (A-E) in the same analogue format and then do the flip test on each. You can save time by just flipping your paper instead of writing out the upside-down versions (also less complicated). Then you can figure out the answer.

As you can see in the drawing, only 15:51, or 3:51 pm can be read the same way upside-down.

\fcolorbox{red}{grey!30}{ Therefore E is the answer.}
1 Like