Divide 40 by half and add 10. What do you get?
The Correct Answer and Explanation is:
Answer: 90
Explanation:
This type of question can be a bit tricky if we don’t read it carefully. The key lies in understanding what it means to “divide 40 by half.” Many people might mistakenly think that dividing by half is the same as taking half of 40, which would be 20. However, dividing by a fraction works differently.
Let’s break it down step by step.
When you are told to “divide 40 by half,” you’re actually performing the operation:
40 ÷ ½
Now let’s recall what dividing by a fraction means. Dividing by a fraction is the same as multiplying by its reciprocal. The reciprocal of ½ is 2. So:
40 ÷ ½ = 40 × 2 = 80
That’s the first part of the problem. We’ve divided 40 by half and arrived at 80.
Next, we are instructed to add 10 to the result. So:
80 + 10 = 90
Therefore, the final answer is 90.
This question is often used as a brain teaser because it sounds simple, but it plays on common misunderstandings of math terminology. The trap lies in the phrase “divide by half.” If someone misinterprets that as “take half of 40,” they would get 20, and then adding 10 would give 30 — which is incorrect.
Understanding how to handle fractions in arithmetic is important. When dividing by a fraction, always remember to flip the fraction and multiply. This rule works with any fraction. For example:
10 ÷ ¼ = 10 × 4 = 40
The more intuitive way to think about it is to ask, “How many halves are in 40?” There are 2 halves in every 1, and 40 ones make 80 halves.
So again, 40 divided by ½ equals 80, and when you add 10, you get 90.
