The fourth grade mathematics application problems and answers Part I
1. The speed of sound is 340m/s, so how many meters can a * * * travel in 50 seconds?
Analysis: Solve with "speed × time = distance".
340× 50 = 17000 (m)
A: A * * * can be paved 17000m.
2. What is the area of a rectangular grassland with a length of 320 meters and a width of 250 meters? How many hectares?
Analysis: 1 ha = 10000 m2.
320×250=80×4×250
=80× 1000
= 80000 square meters
= 8 (hectare)
A: Its area is 80,000 square meters, that is, 8 hectares.
3. A box of 6 egg souffles at the price of 24 yuan. How much does it cost to buy this 150 box of souffles?
Analysis: "There are six souffles in a box" in this question is useless interference information.
150×24= 150×2× 12
=300× 12
= 3600 (yuan)
A: It costs 3,600 yuan.
4. Tables and chairs are 278 yuan/set. The school general affairs office needs to purchase 58 sets. Is it enough to bring 18000 yuan?
Analysis: Judge "Is it enough to bring 18000 yuan?" It can be solved by estimation.
278× 58 < 300× 60 = 18000, that's enough.
A: It is enough to bring 18000 yuan.
5. A company purchased a batch of 42 sets of work clothes at a unit price of 138 yuan/set. Is it enough to bring 5000 yuan?
Analysis: Judge "Is it enough to bring 5000 yuan?" It can be solved by estimation.
138× 42 >130× 40 = 5200 > 5000, which is not enough.
A: 5000 yuan is not enough.
The fourth grade math application problems and answers Part II
1. 100 The water drop weighs about 9 grams. So how much does a hundred million drops of water weigh?
1 100 million, 1000000 100.
1000000×9=9000000 (g) =9000 (kg) =9 tons
A: 1 100 million drops of water weigh about 9 tons.
2. There is a rectangular vegetable field with a length of 200m and a width of150m. Now, if this vegetable field is expanded, its width will remain unchanged and its length will increase by 100 meter. How many square meters will it increase?
200× 150=30000 (m2)
(200+100) ×150 = 45,000 (square meter)
45000-30000= 15000 (m2)
A: It has increased by 1.5 million square meters.
3. Build a highway with a length of 25 kilometers and a width of 40 meters. How many hectares is this highway? How many square kilometers?
Investigation purposes: Calculation of rectangular area and conversion between square kilometers and hectares.
Answer: 25km = 25000m25000× 40 =1000000 (square meter).
1000000 square meters = 100 hectares = 1 square kilometers.
Analysis: pay attention to the unit when reviewing the questions. If the unit is not uniform, it should be converted before calculation.
A rectangular cornfield, 600 meters long and 300 meters wide. If the average yield of corn per hectare is 10 ton, how many tons of corn can this corn field receive?
Objective: to consolidate the calculation of rectangular area, the quantitative relationship of multiplication application problems and the conversion between area units.
Answer: 600×300= 180000 (square meters) 180000 square meters = 18 hectares, 18× 10= 180 (tons).
Analysis: Look at the unit clearly when reviewing the questions. If the units are not uniform, the conversion between different units should be carried out before calculation.
5. There is a square vegetable field with an area of 1 hectare. If its two sides are extended by 100 m, how many hectares will the vegetable area increase?
Objective: To consolidate students' understanding of 1 hectare and improve their ability to solve problems flexibly.
Answer: The side length of a square with an area of 1 ha is 100 m, and the side length of the expanded vegetable field is 100+ 100=200 (m), with an area of 200×200=40000 (m2) and 400000. The area that can be increased is: 4- 1 = 3 (hectare).
Analysis: to solve this kind of problem, you can draw a schematic diagram according to the meaning of the question and then answer it.