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Math diary, Grade Five, 200 words.
Math diary, fifth grade, let's see if it works.

July 3 1 Sunday sunny

Today, my father gave me a task to estimate how many people there are in our community.

How can I finish this task? You can't let me count them one by one, can you? I've been thinking about it for a long time. If I could know how many houses there are in our community, how many families there are in each house and how many people there are in each family, I would be out!

How do I know how many houses there are in our community? As I remember, there is a map of our community. I'll go downstairs and find the distribution map right away. I see that the biggest house number on the distribution map is 16 1. But not all 16 1 buildings are the same height. There are villas, small high-rise buildings and multi-storey apartments. There are three small high-rise buildings, 1 1 floor, each with two house numbers; There are 10 villas with 1 house numbers respectively. The rest are all six-story multi-storey apartments. How many house numbers are there in a multi-storey apartment? It should be calculated as follows:161-3× 2-10×1=145.

Knowing the number and floor of the house, I can calculate the number of households, but how many people should each household count? I assume that there are three people in each household. Total number of villas = 10× 3 = 30 people; The total number of people in small and high floors = 3× 2×11× 2× 3 = 396; Total number of people in multi-storey apartment: 145× 6× 2× 3 = 5220. So the total number of people in the community is 30+396+5220 = 5646.

I feel very happy after finishing my father's task. I feel quite capable, and it is not easy to count the people living in the community.

It will be fine on Saturday, August 15.

One sunny day, my parents took me to buy stationery. When I arrived at the stationery store, I saw all kinds of book covers, including Miss Rabbit's, Pleasant Goat's and Big Big Wolf's, and Blue Bear's ... I looked at the price list: 5.00 yuan for small book covers and 6.00 yuan for large book covers, and I immediately took 5 small book covers and 4 large book covers. Walking, I saw a beautiful pencil case, each 6.00 yuan. Mom said, "There are several pencil cases, so I still want to buy them!" " ""just the last one! "I said imploringly." Well, just the last one! ""hmm! " Say that finish, I picked up the pencil case I picked and put it in the basket.

When I got to the cashier, my father said, "Let's calculate first. How much do these cost?" I counted: "5×5+6×4+6, hmm ... 25+24+6=55 yuan!" Mother handed 55 yuan to the shop assistant, and our family went home happily.