Math thesis, grade five-I have some opinions on two-digit multiplication. Among them, not all of them need column vertical calculation. There are many kinds of two-digit multiplication. Let me name five of them first. 1. The sum of digits is equal to 10, and the ten digits are the same. Second, ten digits add up to 10, and the digits are the same. Third, the addition of ten digits and one digit is neither equal to 10, nor the same, which is irregular. Fourth, the sum of digits is equal to 10, but the ten digits are different. Fifth, the ten digits add up to 10, but the digits are different. Sixth, of course, I don't know everything, but I know a little. At least I can write the first three simple methods.

Let me list a few questions: the first question, 86? 84= how much. 86 and 84 bits add up to 10, and the ten digits are the same. This is the first case. It can be calculated as follows: 8+1= 9,8? 9=72, ending 4? 6=24,8? The result of 9 is hundreds of products, 4? The result of 6 is the ten digits and one digit of the product. The product of this problem is 7224. Second question, 34? 52, which belongs to the third kind, can be multiplied by addition and completed in three steps. The first step is 2? 4=8, bit multiplication, product tail is 8. Step two, use 4? 5+3? 2=26, cross multiply and add, and write 6 as 2. Step 3, multiply 10 by 3? 5 = 15, 15 plus 2 equals 17, and the product of this problem is 1768. The third question, 68? 48, belonging to the second category, the sum of ten digits is equal to 10, and the digits are the same. With 6? 4=24, 24+8=32, and the product of thousands and hundreds is 3 and 2. Finally multiply, 8? 8=64, ten digits and one digit are 6 and 4, and the product of this problem is 3264.

And of course, the finger algorithm. Without saying much, I won't introduce them one by one. After reading my method, do you think it is mine or the old-fashioned method in mathematics?

Today, my mother is going to buy a light bulb. When I arrived at the supermarket, I found that there are two kinds of light bulbs in the supermarket: one is energy-saving light bulbs and the other is ordinary light bulbs. Although the energy-saving light bulb only needs one degree of electricity for 200 hours, which is 170 hours more than the ordinary light bulb, it needs 5 yuan. An ordinary light bulb costs only 1 yuan, which is cheaper than energy-saving light bulbs by 4 yuan, but it uses one degree of electricity every 30 hours.

Mom asked me:? Test you, if I want to buy a light bulb to go home, what kind of light bulb is the most cost-effective?

I thought about it and said unhurriedly, it can be calculated like this:

5? 1=530? 5= 150 (hours) 200 hours > 150 hours

You can also calculate it like this:

5? 1=5200? 5=40 (hours) 30 hours

From these steps, it can be concluded that energy-saving light bulbs save money. ?

Mom asked me again:? It's good. Think again, is there any other calculation method?

I thought about it and said word for word: Can I use the percentage I just learned this semester? To calculate:

5/200? 100=0.025? 100=2.5

1/30? 100? 0.033? 100=3.3

3.3 & gt2.5

Or calculate it like this:

200/5? 100=40? 100=4000

30/ 1? 100=30? 100=3000

4000 & gt3000

So energy-saving light bulbs are also cheap. . ?

My mother and I bought more cost-effective energy-saving light bulbs and went back.

After this incident, I understand: there is mathematics everywhere in life? This truth.

The fifth grade math thesis three is full of math. I came to the supermarket today and verified this truth. By comparison, I also found that selling some things in sets is more expensive than buying them individually.

I came to the shelf with sausages. There are several packages of sausages on the shelf, with the same brand and weight. There are 10 sausages in it, each package is 4.30 yuan. Do you want to buy a pack or a slice? I hesitated. Suddenly, my mind turned and I understood. Just compare and see which one is cost-effective. So I started to calculate: If you buy 10 pieces in retail, each piece costs 40 cents, * * * is 4 yuan, and the whole package costs 4.30 yuan, which is 30 cents more, so the suit is more expensive than the bulk.

I went to the beverage counter and bought a 250ml bottle of herbal tea 1.75 yuan, but the price of the whole box 16 bottles on the container was 30.4 yuan. If you buy 16 bottles at the unit price of 1.75 yuan, you only need 28 yuan. Obviously, it costs less 2.4 yuan to pay for the bottle than the whole box. 3 10ml canned beverage of Wang Lao Ji, one bottle from 3.4 yuan, whole case 12 bottle of 42 yuan. If you buy 12 bottle at the unit price of 3.4 yuan, you only need 40.8 yuan, which is cheaper than the whole case 1.2 yuan; The same variety, a box of 24 bottles costs 90.7 yuan. If you buy 24 bottles at the retail price in 3.4 yuan, it will cost 8 1.6 yuan, which is 9. 1 yuan less than the whole case. Next to the beer, the unit price per can is 2.9 yuan, 24 bottles are 69.6 yuan, but the supermarket charges 76.8 yuan. The extra 7.2 yuan can buy two more cans of beer.

Students, mathematics is mysterious and flexible. Besides what I just mentioned, there are many kinds of mathematics in life! So learning mathematics is to apply it to real life to solve practical problems, and mathematical problems arise from life. I hope that students can learn mathematics in their lives and use mathematics in their lives. Mathematics is inseparable from life. If they study thoroughly, they will naturally find that mathematics is actually very useful.