Скачать или смотреть Brain Twister - How Many Kids Ate All Four Types Of Fruits?

There are 100 kids in a class. The teacher is collecting data about what kind of fruits they did eat for lunch on that day. According to the statistics, 85 kids ate apples today, 80 kids ate oranges, 75 kids ate bananas and 70 kids ate pears. The teacher want to know how many kids ate all types of four fruits, namely, apple, orange, banana and pear. If you are the teacher and you don't want to do complex calculations, what is the quickest way to get the result?

This video will pause for 30 seconds for you to quickly think about the answer. You can also pause the video if you need more time to think about it. Good luck.

Now it is time for the answer. This problems seems to be hard if we want to calculate the result directly. Maybe we can try thinking it from a different angle. Since 85 kids ate apples today, that means there are 100 - 85 = 15 kids who didn't eat apples today. Similarly, we can know that there are 100 - 80 = 20 kids who didn't eat oranges today. Also, there are 100 - 75 = 25 kids not eating bananas today, and the number of kids who didn't eat pears are 100 - 70 = 30. If we sum these numbers up, we will know that there are 15 + 20 + 25 + 30 = 90 kids who didn't eat at least one type of fruits. As a result, the remaining number, which is 100 - 90 = 10, should be the number of kids who ate all four types of fruits for lunch today.

Did you get the correct answer within the 30-second pause?