The riddle is as follows:
The figure from below represents a set of roman numerals wrote in such a way that the sum is not correct.
The numbers are arranged as:
How many matches minimum should me moved to make operation correct?
The alternatives given in my workbook are as follows:
I found this puzzle in my riddles book Logical fun and challenges from 2000's. It seems to be an adaptation from an old IQ test, can't say which exactly.
This problem has an official solution from my workbook, and it is presented in the figure from below.
Therefore it indicates that the answer is 2, which to me, doesn't make any sense.
The reason for that is I can't recall any weird roman numeral with the shape indicated in the official answer. I'm referring to the letter T. Could it be that I have the wrong interpretation?
Is there a way to get this right?
Can someone help me here? Perhaps with a guideline for which matchstick someone should look for initially, or which part of the operation should be changed?
For example, I noticed that a sum usually (not always) should be changed for another operation. Sometimes swapping sum by a subtraction is right because the number on the left side would require less movements. I think it also helps to count the number of matchsticks, so that you can get a hint on what is the greatest number which can be formed by using these given the operations you can make. I mean multiplication. I also noticed that, there isn't a way to make a division with the matchsticks because there isn't a set of dots which you could use to make that operation. Although you could make the division L shape which you put below the divisor or dividend in the long hand division algorithm, but this of course requires moving additional matchsticks, and there is finally multiplication which sometimes could help.
So overall, does a rule of thumb for for this exist? And more importantly, is the solution method accurate?