Today, Teacher Yuan talks about how to find the least common multiple. The teacher said, "If two books are prime numbers, their product is their least common multiple." I think: the number smaller than their product may also be their common multiple!

After class, I calculated several pairs of prime numbers with my exercise book, but their least common multiple is equal to their product. It's amazing! The truth of mathematics is amazing! I will study hard and master more skills.

My discovery

Students, have you made some casual discoveries in math study like me? Now I will introduce some of my findings.

If you want to calculate a multi-digit multiplied by 5, do you want to calculate it vertically? But I can do it with my mouth, because I found a little trick. Do you want to know? Let me tell you: calculate the product of 48532×5, first find this number 485320, and then divide it by 2. Can I take it orally? 242660 This is the product of 48532×5. Do you know why? I first expanded the original number by 10 times, and then reduced it by 2 times. Is it equivalent to expanding five times? Have you mastered this little trick?

I also found the same thing: multiplying a number by 1.5 only needs to add half to itself. (think about why? How about a number multiplied by 15? Use the method just now to add one more step-you have already thought of it, and then expand it by 10 times!

I also found a multi-digit, and the last two digits meet this requirement: ten digits are odd and one digit is 5. Multiplied by 5, the last two digits of the product must be 75. I think why is this? Because the unit of multiple digits is multiplied by 5 to get 25, the unit of product is 5, which is the tenth power of 2, and the odd number of ten is multiplied by 5 to get 15. This 5 must be added with the 5 to be written on the ten, so the product must be the tenth power of 7 and the tenth power of 5. In the same way, it is not difficult for you to deduce that a multi-digit number is even in ten digits and 5 in one digit. It is multiplied by 5, and the last two digits of the product must be 25.

Can this discovery be explained by an ingenious algorithm of multiplying numbers by 5 that I mentioned earlier? Think about it, they are the same, because after this number is expanded by 10 times, the last two digits are 50, and then divided by 2, there may be a remainder of 1 in the hundreds, and when combined with 50, 150÷2=75 is the last two digits, or there may be no/kloc-0 in the hundreds.

Students, is my little discovery insignificant? But I am very proud, this is the result of my own observation and thinking. Aren't great discoveries made up of these bits and pieces? Students, let's be a diligent thinker and discoverer!