In the world, everything has two sides. The rich experience of adults determines that they see things more comprehensively. The following is the answer to the fourth grade math summer homework, I hope everyone will read it carefully!
1 fourth grade, volume 2, answers to summer math homework
P3 approximations are usually in thousands, tens of thousands, millions, tens of millions and billions.
P5 The approximate number of a natural number is 500 million, the maximum number can be 549,999,999, and the minimum number can be 450,000,000.
P9 wheat was placed in 28 grids, once breaking through 1 100 million grains; About 92233720368 million tablets will be put in the 64th box.
P 1 1 discriminant, 3 and 4 are wrong, others are right.
P 15 angle: angle 4=60 degrees, angle 5=72 degrees and angle 6=36 degrees.
P 19 drawing, pay attention to draw a vertical line and mark it with right-angle symbols.
P20: The trapezoid has 5 and 6, and the axisymmetric figure is 1, 3, 4, 5.
P23 Fill in 360m2 =0.036 hectare.
Receipt: RMB 38,650.00 in words.
P24 Select (3) Select 9.
P3 1 Think about it (1) Choose A and B.
P43 matching formula: 23x4 = 9228x11= 30817x14 = 238.
P45 formula 209x46 = 9614372x38 =14136315x41=12915.
P47 Outmost treatment result: (10- 1)x4=36 (pots), with a total of 10x 10= 100 pots.
Draw a picture and calculate (21-1) x50 =1000 cm =10m (260+10)/37 =/kloc-.
The logarithm discrimination of P50 is 12, 16 and 12.
P53 14th century, China people.
P55 processing score 142-34= 108 (block) 108/2=54 (block) 54/ 18=3 (times).
P56 formula calculation (3) difference: 75- 15=60 Kobayashi is 60/(3- 1)=30 years later: 30- 15= 15 years later.
P58 Fill in one, two (5) and add (5) zeros at both ends of 48 to make 4000008.
The divisor and divisor in P602 table are extended by opposite multiples (except 0) at the same time, and the quotient remains unchanged.
P6 1 Think about it. (3) It took 2.5 hours to ride a bike, with an average of12km per hour.
Pages 62 and 63
1. True or false
( 1)? Water can dissolve some solids as well as gases and liquids. )
(2)? Rock sugar still exists after it is dissolved in water. )
(3)? Put some lard in the hot vegetable soup, and it will break down into smaller ones. )
(4)? When water evaporates, substances dissolved in water still exist. )
(5)? Substances insoluble in water may not sink to the bottom of the water. For example: vegetable oil. )
(6)?
(7)?
(8)? Sound can travel in water. )
(9)? Sound can travel in all directions. )
( 10)? (No air transmission)
2. Insolubles are: flour, rape and clods.
3. Small experiment
Tip: Try to put as much salt as possible when doing small experiments, and choose bottles with as small a mouth as possible, so that the observation results will be more obvious.
The results show that the water level rises obviously when the salt content is large and the bottle mouth is small. If the salt content is small and the bottle mouth is large, the water level will not rise obviously, but it will rise in principle and the water level will also rise.
4. I hope to read the content of the small materials carefully and talk about it in practice.
Page 64
1. Multiple choice problem
( 1)c (2)a (3)c (4) c
2. True or false
All seven questions?
Explain question (3): (Pay attention to the difference)
Connecting two batteries in series can make the bulb emit brighter light.
Connecting two bulbs in series can make the small bulb emit darker light.
3. Small experiment
(1) Explaining the principle of homemade wind instruments
Test tube: the water level is low, the test tube vibrates quickly and the sound is high. On the contrary, the water level is high, the test tube vibrates slowly and the sound is low. (The figure should show bass. )
Suction pipe: short air column, fast vibration and high sound; Long air column, slow vibration and low sound. The picture should be high and low. )
(2) Small activities
The brine heating bulb turns bright and the brine cooling bulb turns dark. The reason is that the increase of salt water temperature accelerates the molecular activity, and the electrolyte in water increases, which increases the conductivity of water.
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