# Answer: What is the answer? 7 + 7 ÷ 7 + 7 x 7 – 7

Last week I posted a second mathematical challenge, and today I will go through the answer.

If you have not answered the poll on the second challenge, please go and do that now:

So here is the question again:

And here is the answer: 50 7 + 7 / 7 + 7 x 7 – 7

Did you get it right? If not, here are the steps.

Remember your order of operations using your favourite mnemonic: BIMDAS, PEDMAS, My Dear Aunt Sally, etc. They all tell you that Multiplication and Division must be done at the same time, but before Addition and Subtraction. Then Addition and Subtraction can be done be at the same time.

i.e. My Dear Aunt Sally (MDAS) is actually the same as Dear My Sally Aunt (DMSA).

After the order of operations is handled, just calculate from left to right. So….

• 7 + 7 ÷ 7 + 7 x 7 – 7

Do Multiplication and Division first.

• 7 + 7 ÷ 7 + 7 x 7 – 7
• 7 + 1 + 49 – 7

Then finish with Addition and Subtraction (from left to right).

• 7 + 1 + 49 – 7
• 8 + 49 – 7
• 57 – 7
• 50

You could also simplify the equation and cancel out the positive 7 and negative 7.

• 7 + 1 + 49 – 7
• 1 + 49
• 50

Please note that if you type this into a simple calculator and so ignore the order of operations and just calculate each operation individually from left to right, you will get a different but incorrect answer.

• 7 + 7 ÷ 7 + 7 x 7 – 7
• 14 ÷ 7 + 7 x 7 – 7
• 2 + 7 x 7 – 7
• 9 x 7 – 7
• 63 – 7
• 56, but this is still wrong as you must multiply and divide first.

It was good to see that most people got this second challenge correct.

Hopefully, that should end the maths lessons for a while. 🙂

David