Answer: Only for genius ?? 3 – 3 x 6 + 2 = ??

After posting Trending: Only for genius ?? 3 – 3 x 6 + 2 = ?? yesterday, I had to post a follow up article with the correct answer.

Even with the hint about remembering the order of operations, people still got it wrong on my poll. If you haven’t done the poll yet, click on the link above and respond.

The question was

The correct answer is as follows:

1. Question: 3 – 3 x 6 + 2
2. Multiplication first: 3 – 18 + 2
3. Left to right: -15 + 2
4. Answer: -13

So what do you get if you type it into a calculator (physical or app)?

That depends on if the calculator is simple and calculates as you type, or if it is smart and waits for the entire equation to be entered and the equals button pressed.

On my Windows 10 Mobile phone, the calculator app can behave in both ways.

In Scientific mode, it allows the entire equation to be entered and so correctly calculates the answer as -13 using the “Order of Operations” rules (same as above).

In Standard mode, it calculates as you type and so incorrectly gives the answer as 2. The way to think of it is that it inherently presses equals each time you press an operation button. This is just left to right calculation and ignores the “Order of Operations” rules.

1. 3 = 3
2. 3 – 3 = 0
3. 0 x 6 = 0
4. 0 + 2 = 2

If your calculator behaves in this simple way, you would need to apply the rules yourself. Here are the buttons to press:

• 3 x 6 = MS
• 3 – MR + 2 =

If your calculator has brackets or parentheses buttons you can use them instead of the Memory buttons to achieve the same effect.

• 3 – ( 3 x 6 ) + 2

Looking at the poll results from the previous article, there are a number of incorrect answers being selected, so I thought I would try to identify the actual equations that would give those incorrect answers (changes highlighted in red):

• -17 = 3 – ( 3 x 6 + 2 )
• 0 = ( 3 – 3 ) x ( 6 + 2 )
• 2 = ( 3 – 3 ) x 6 + 2
• 8 = 3 – 3 + 6 + 2
• 13 = – 3 + 3 x 6 – 2
• 17 = – 3 + 3 x 6 + 2

Hope this all makes sense. Here endeth the lesson. :)

David

This article was originally posted on http://www.winthropdc.com/blog.