Solving logic problems grade 4
Logical problems are completely different. This can be a simple classic in the form of word problems, or there can be tasks involving ingenuity. Also puzzles, algorithms, determination of truth and lies, combinatorial and many other different logic problems.
Word problems like “Counting legs and heads” are very popular in math competitions and in tasks with an asterisk in the textbook.
Geese and sheep live on the farm. In total they have 40 heads and 94 legs. How many geese live on the farm? and how many sheep?
Let's deal with all the legs first. We know that a sheep has four, and a goose has two. Let's calculate this if everyone has two legs. Since there are 40 goals, it turns out:
40 • 2 = 80 legs.
According to the condition, there are only 94 legs in the problem, let’s find the so-called “extra” legs:
94 — 80 = 14.
If these 14 legs are extra, then they belong to four-legged sheep, and now we can determine the number of sheep:
14:2 = 7 sheep.
Now all that remains is to calculate how many geese there are on the farm. To do this, simply subtract from the total number of heads those that belong to sheep:
40 - 7 = 33 geese.
Answer: 7 sheep and 33 geese.
Another equally popular task is “handshakes”.
Vanya met his friends Petya, Masha and Kolya on the playground. When they met, they all shook hands. How many handshakes were there during the meeting?
In fourth grade, it is most convenient to solve such problems using a diagram. We denote each person with a dot. Then from each point we draw segments to those with which we need to shake hands. We count the number of segments, it will be the answer to the problem.
Answer: six handshakes.
A new five-entrance house with 10 floors was built. There are four apartments on each floor. A number was hung on each door of the apartment. How many digits 2 are needed for all apartment numbers?
First, let's calculate how many apartments there are in the house:
10 • 5 • 4 = 200.
Let's count how many times the number two appears before a hundred: 2, 12, 22, 32, 42, 52, 62, 72, 82, 92. Total ten times. From one hundred to 199, the number 2 will also appear ten more times. That’s a total of 20 times.
In the tens place there are 10 times up to 100 and another 10 up to 199, and one two in 200. We get:
20 + 20 + 1 = 41 digits.
Answer: 41 digits are required.
The centipede has 80 legs. By winter, she bought 12 pairs of boots. Still, 14 legs were left without boots. How many pairs of old boots did the centipede have before she bought new ones?
- 12 • 2 = 24 feet in new boots
- 80 - 24 = 56 feet barefoot and in old boots
- 56 - 14 = 42 feet in old boots
- 42:2 = 21 pairs of old boots.
Answer: The centipede had 21 pairs of old boots.
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so UNT / Lesson developments / Lessons in Mathematics
Mathematics 4th grade. Topic: Solving logical problems
22.09.2014 11526 1972
Target:
learn to solve logic problems
Tasks:
· work on developing the skill of solving logical problems;
· Develop logical thinking, attention, memory, intelligence;
· Foster a culture of communication.
Equipment:
presentation for the lesson, cards, stickers, markers
Plan
I.
Org.
moment. II.
The main part of the lesson
- What is the name of the object?
— What does the word “logic” mean?
(Logic is the science of correct thinking. The art of reasoning. The science of sanity.
In any science, logic is one of the main tools)
— What helps develop logic thinking?
— Lesson topic: “Solving logical problems”
To find out the motto of our lesson you need to guess the puzzles
— Lesson motto: “Logic is mental gymnastics.”
— What tasks do you already know?
(puzzles, charades, rebuses, crosswords, drawing problems, logical mini-tasks, problems on number systems, linguistic problems, problems with incomplete conditions, joke problems, transfusions, etc.)
1) “Brain gymnastics”
· Underground Railroad?
· The main song of the state?
· How many times does the sun rise a year?
· How many minutes are in 3 hours?
· What is heavier than a pound of fluff or a pound of iron?
· What is the name of the only bird on Earth that can fly backwards?
· When is the day shorter in winter or summer?
· One and a half pike perch cost one and a half rubles, how much do thirteen pike perch cost?
· How many 9s are there in the row from 1 to 100?
· Which animal has the loudest voice?
The loudest animal is the sea whale, which makes the loudest sounds in the world using low-frequency impulses. The noise can reach an intensity of up to 188 decibels. Simply put, the cries of blue whales can be heard at a distance of 800 kilometers. Plus, it is the largest animal in the world.
2) Checking homework.
Goal: check the solution to puzzle problems. Puzzles. (Each group prepared a puzzle, decide, mutual assessment.)
I have also prepared tasks for you, tasks to develop concentration.
Problems with matches: “Fish”, “Glass with a cherry”, “Squares”. 3.) Work on the topic of the lesson
Speech by T. Tomashevsky, participant of the III Regional Scientific and Practical Conference of Schoolchildren.
1. Types of tasks
2. Algorithm for solving logical problems
3. Ways to solve logical problems
See the downloadable file for the full text of the material.
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