To make a cream cake, you need 7.5 grams of cream each. How many cakes can 50 grams of cream make?
50 ÷ 0.75 = 66.666 ...≈ 67 (pieces)
2. Error cause analysis:
When finding the approximate number of cakes in this question, many students often get 67 cakes by rounding, regardless of the actual life situation. In real life, after eating 66 whole cakes, the remaining 50 grams of cream is not enough to make a complete cake.
3. Ideas for solving problems:
To solve this problem, we should consider the real life situation. Each cake needs 7.5 grams of cream, 50 grams of cream can make 50÷0.75=66 (blocks) ... 50 grams, and the remaining 50 grams of cream is not enough to make a complete cake, so it should be discarded and the tail removed to solve the problem.
4. Problem solving process:
50÷0.75≈66 (piece)
A: 50 grams of cream can make up to 66 such cakes.
5. Variant correction:
(1) Each suit is made of 2.2m cloth. How many sets of such clothes can 50m cloth make at most?
(2) How many footballs can Uncle Wang buy per 45 yuan with 300 yuan?
(3) Each oil pot can hold 3 kilograms of oil. How many of these oil pots should be prepared to hold 40 kilograms of oil?
(4) If a pile of goods is 13.6 tons, how many times will it be transported by a truck with a load of 4 tons?
(5) The kindergarten bought 50 cakes, every 8 cakes were packed in a box. How many boxes do you need at least?
The first volume of fifth grade mathematics is prone to mistakes. It is more perfect to write the wrong question and copy it before answering it (with an answer).
Example:
1.***********
Answer: * * * *
Wrong knowledge points: * * * *
2.*****
Answer: * * *
The answers to the error-prone exercises set in the second volume of the fifth grade are not written anywhere in Khan's publications.
I want fifth grade math to be easy to make mistakes. Grandpa is seven times as old as Xiaoli this year. A few years later, grandpa was six times as old as Xiaoli. A few years later, grandpa was four times as old as Xiaoli. Ask grandpa how old he is this year.
2. The circumference of a semicircular piece of paper is 10.28 decimeter. What's its square decimeter?
The perimeter of the semi-circular flower bed is102.8m.. What is its area?
1. Determine whether the following questions are correct, tick "√" for the right and "3" for the wrong.
(1) The formula for calculating the area of a circle with a diameter of 10 mm is 3. 14×( 10÷2)? ; . ()
(2) The circumference and area of a circle with a radius of 2 cm are equal. ()
(3) Tie the cow to a stake. The rope between the stake and the cow is 3 meters long, and the maximum area where the cow can graze on the ground is 28.26 square meters. (not counting the place where the rope is tied)
()
6 cm
(4) Area: 3.14× 62 = 3.14×12 = 37.68.
()
2. Measure the data needed to calculate the semicircle area, and keep the number of whole centimeters when measuring. Then calculate its perimeter and area.
(1) What is the circumference of a semicircle? (2) area of semicircle:
3. 14×223. 14×2+2×2
r=2cm=3. 14×4=6.28+4
= 12.56 (cm2) = 10.28 (cm)
3. The circumference of a circle is 25. 12m. What is its area?
Known: c = 25.12m: S=?
r = 25. 12(2×3. 14)S =πR2
=4 (m) =3. 14×42
=50.24 square meters
4. An annular iron sheet with a radius of 7 cm in the outer circle and 0.5 decimeter in the inner circle. What is the area of this ring?
Known: R=7 cm =0.7 decimeter r=0.5 decimeter Q: S=?
S ring = π× (R2-R2)
3. 14×(0.72-0.52)
=3. 14×0.24
=0.7536 (square decimeter)
Three. Consolidate development.
1, thinking question p7 1(8)
A rope is 3 1.4m long. Which is bigger, enclosing a rectangle or a square or a circle? (Group discussion, discuss the size of the area)
(1) bound into a rectangle: 3 1.4÷2= 15.7(m) (sum of length and width)
Length × width = area
When the length and width are closer, the area will be larger. When the length and width are equal, the area of a square is the largest.
(2) form a circle
Diameter: 31.4÷ 3.14 =10 (m)
Radius:10 ÷ 2 = 5m
Area: 3.14× 52 = 78.5m2.
I hope it helps you.
Please adopt it. Thank you.
Are there any mistakes in the fifth grade math? Yes! Buying a book called "Top Students" is very good, with error-prone questions, explanations and analysis.
The circumference of a semicircular piece of paper is 10.28 decimeter. What's its square decimeter?
The perimeter of the semi-circular flower bed is102.8m.. What is its area?
1. Determine whether the following questions are correct, tick "√" for the right and "3" for the wrong.
(1) The formula for calculating the area of a circle with a diameter of 10 mm is 3.14× (10 ÷ 2)&; sup2。 ()
(2) The circumference and area of a circle with a radius of 2 cm are equal. ()
(3) Tie the cow to a stake. The rope between the stake and the cow is 3 meters long, and the maximum area where the cow can graze on the ground is 28.26 square meters. (not counting the place where the rope is tied)
()
6 cm
(4) Area: 3.14× 62 = 3.14×12 = 37.68.
()
2. Measure the data needed to calculate the semicircle area, and keep the number of whole centimeters when measuring. Then calculate its perimeter and area.
(1) What is the circumference of a semicircle? (2) area of semicircle:
3. 14×223. 14×2+2×2
r=2cm=3. 14×4=6.28+4
= 12.56 (cm2) = 10.28 (cm)
3. The circumference of a circle is 25. 12m. What is its area?
Known: c = 25.12m: S=?
r = 25. 12(2×3. 14)S =πR2
=4 (m) =3. 14×42
=50.24 square meters
4. An annular iron sheet with a radius of 7 cm in the outer circle and 0.5 decimeter in the inner circle. What is the area of this ring?
Known: R=7 cm =0.7 decimeter r=0.5 decimeter Q: S=?
S ring = π× (R2-R2)
3. 14×(0.72-0.52)
=3. 14×0.24
=0.7536 (square decimeter)
Three. Consolidate development.
1, thinking question p7 1(8)
A rope is 3 1.4m long. Which is bigger, enclosing a rectangle or a square or a circle? (Group discussion, discuss the size of the area)
(1) bound into a rectangle: 3 1.4÷2= 15.7(m) (sum of length and width)
Length × width = area
When the length and width are closer, the area will be larger. When the length and width are equal, the area of a square is the largest.
(2) form a circle
Diameter: 31.4÷ 3.14 =10 (m)
Radius:10 ÷ 2 = 5m
Area: 3.14× 52 = 78.5m2.
I wish you good results in the exam.
The fifth grade book 12, a and b are natural numbers, A÷B=0. 1, the greatest common factor of a and b is (a), and the least common multiple of a and b is (b). 13, a=2×3×m, b=3×5×m(m is a natural number, m≠0). If the greatest common factor of A and B is 2 1, then M is (7) and the least common multiple of A and B is (2 10).
14, A =2×2×a×b, B =2×a×b×3, a, b, a and b are all natural numbers greater than 1, and the least common multiple of a and b is (12ab).
15, fill in the number as required. (1) Fill in a number in brackets, so that the greatest common factor of these two numbers is 1. 3 and (17) 8 and (17) 15 and (17).
(2) Fill in a number in brackets so that the least common multiple of these two numbers is the filled number. 5 and (10) (24) and 12 (48) and 24.
(3) The minimum common multiple is 24 () and the maximum common factor is 6 (). (There is something wrong with the title)
Judge1√ 2× 3 √ 4 √ 5× 6 √ 7 √ 8 √ 9 √1√12 √13 √ 65438+.
Honey, ask again if you don't understand. I'm in grade five, too
(People's Education Edition) The first volume of the fifth grade mathematics is easy to make mistakes and the units are easy to be inconsistent. For example:
Xiao Wei's living room area is 25 square meters. How many tiles do you need for a floor with a side length of 60 cm? If each floor tile is 15 yuan, how much does it cost to buy these floor tiles?
The formula of solving mathematical problems in the first volume of the fifth grade is easy to be wrong 5x-40 = 202x+20 = 40x-0.5x =1x+0.2x = 0.723x+x = 30x ÷ 4.5 = 20.
2.7X- 1.6 = 38.9 6X-0.4×6 = 9.6