Puzzling maths puzzles …


On a roll here. Two posts in one day, whatever next?

This one is directly attributable to Facebook. You often get people posting maths puzzles on Facebook. The kind of thingpuzzle where you get some equations and you have to work out how they get the answers. It is basic Algebra. I love reading these posts, working out the correct answer and then trying to explain to people about the ‘mathematical order of operation’. This one follows the usual pattern but is a little different. Initially, it is easy to work out what the Snowflake image is worth, it must have a value of 10 for the first equation to work. From that deduction the cane must have a value of 5 with the wine glasses having a value of 2. Easy. Then you have to work out the last equation and here, the composer has added a twist by putting a multiplication sign in the equation. This is where the order of operation comes in. From my school days, it was always drummed into me that multiplication comes before addition, unless the addition is held within parenthesis.

Without looking carefully people will come up with the answer 70, 17 or 25. However, there is another twist here. In the last equation there is an image of a single wine glass. I did not see this at first and came up with 25 :- 10 x 2 = 20 + 5 = 25. But this puzzle has fooled many people. The answer a large number have come up with is 15. Many people have made the assumption that the image of the single glass has the value of 1. For me, this is an unsafe assumption. There is no way of safely giving the value of 1 to the single glass.  It can have any value except 10, 5 or 2. There is nothing to stop the single glass having the value of 99 for example which would give the last equation the result of 995. It fooled me at first look, but in actual fact, with the information given, a solution cannot be found.

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