This is viral math brainteaser from Japan.
It is Easy But Tricky
9 – 3 ÷ 1/3 + 1 = ?
Most people will find answer as 9 but the Correct Answer is 1
Explanation:
The most common mistake is writing the 1/3 as: 9 – 3 ÷ 1/3 + 1
Most calculators will not group the 1/3, so the calculator evaluates: 9 – 3/1/3 + 1
= 9 – 3/3 + 1
= 9 – 1 + 1
= 9
The correct answer is found by grouping 1/3 with parentheses and following the order of operations, with division taking precedence.
9 – 3 ÷ (1/3) + 1
= 9 – 9 + 1
= 0 + 1
= 1
Source (English)
http://en.rocketnews24.com/2015/12/05/does-this-math-problem-prove-that-japans-20-somethings-are-getting-dumber/
Sources (Japanese)
http://www.j-cast.com/2015/12/03252296.html?p=all
http://www.yukawanet.com/archives/4618548.html
4 replies on “Viral Math Problem – Try It”
You answer is still wrong the order of operation has addition BEFORE subtraction so the answer is -1 .. 9 – 9 + 1 …. 9 -10 = -1 … you should always follow the order of operations PEDMAS (BEDMAS)
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Personally think my answer is better and clearer:
Most people will find answer as 9 but the Correct Answer is 1
Explanation:
The most common mistake is writing the 1/3 as: 9 – 3 ÷ 1/3 + 1
rather than treating it as 1/3 (one third – a fraction)
Most calculators will not group the 1/3, so the calculator evaluates: 9 – 3 ÷ 1 ÷ 3 + 1
= 9 – 3/3 + 1
= 9 – 1 + 1
= 9
But if you remember back to school you would do this equation as:
3 1
9 – ( – ÷ – ) + 1
1 3
3 3
= 9 – ( – x – ) + 1
1 1
Remember that when you change a division to a multiply you turn the
fraction upside down. You can no just multiply the numerators and denominators to give:
9
= 9 – ( – ) + 1
1
= 9 – 9 + 1
= 1
Note you will also get the correct result if you followed my hint and used 0.33333333 instead of 1/3
in this case you get
9 – 3 ÷ 0.3333333333 + 1
= 9 – 9 + 1
= 9
(note you need to round it as the 1/3 in decimal is actually 0.333 repeator)
Thank you for your explanation. I will try to edit post to simplify explanation.