问题1.有两种包装的汽水:
(i)一个锡罐,其长为5厘米,宽为4厘米,高度为15厘米的矩形底,以及
(ii)一个直径为7厘米,高度为10厘米的圆形底座的塑料圆筒,哪个容器的容量更大,增加多少?
解决方案 :
Given that,
The tin can with a rectangular base:
Length= 5 cm,
Breadth = 4 cm,
Height = 15 cm
The plastic cylinder with circular base:
Diameter = 7cm
So the radius of the base = 7/2 cm = 3.5 cm
Height = 10 cm
Now we find the volume of both cans:
Capacity of the tin can = l × b × h = (5 × 4 x 15) cm3
Capacity of plastic cylinder = πR2H = 22/7 × (3.5)2 × 10 cm3 = 385 cm3
Difference in Capacity = (385 – 300) = 85 cm3
Hence, the plastic cylinder has greater capacity.
问题2:太阳穴的柱子是圆柱形的。如果每个支柱都有一个半径为20 cm,高度为10 m的圆形基座,那么要建造14根这样的支柱需要多少混凝土混合物?
解决方案:
Given that,
Radius of the base of a cylindrical pillar= 20 cm
The height of the cylindrical pillar = 10 m
Find how much concrete mixture would be required to build 14 such pillars
So
Volume of the cylindrical pillar = πR2H
= (22/7 × 202 × 1000)
= 8800000/7
= 8.8/7 m3
The volume of 14 pillars = 8.8/7 × 14 = 17.6 m3
Hence, the volume of the 14 pillars = 17.6 m3
问题3.圆柱形木管的内径为24厘米,外径为28厘米。管道的长度为35厘米。如果1 cm 3的木材的质量为0.6 gm,请找到管道的质量。
解决方案:
Given that,
The inner diameter of a cylindrical wooden pipe(d1) = 24 cm
So, the inner radius of a cylindrical pipe(r1) = 24/2 = 12 cm
The outer diameter of a cylindrical wooden pipe(d2) = 28 cm
So, the outer radius of a cylindrical pipe(r2) = 28/2 = 14 cm
Height of cylindrical pipe (h) = 35 cm
Find the mass of the pipe, if 1 cm3 of wood has a mass of 0.6 gm
So,
The Mass of pipe = Volume x density
= π(r22 – r12)
= 22/7 x (142 − 122) x 35 = 5720 cm3
Mass of 1 cm3 wood = 0.6 gm
Mass of 5720 cm3 wood = 5720 × 0.6 = 3432 gm = 3.432 kg
问题4.如果圆柱体的侧面为94.2 cm 2且其高度为5 cm,则找到:
(i)它的底面半径
(ii)气瓶的容积[使用pi = 3.141]
解决方案 :
Given that,
The lateral surface of a cylinder = 94.2 cm2
The hight of the cylinder = 5cm
(i) Find the radius of its base
Let’s assume that the radius of cylinder be ‘r’
Curved surface of the cylinder = 2πrh
94.2 = 2 (3.14)r(5)
r = 3 cm
Hence, the radius of the cylinder is 3 cm
(ii) As we know that
The volume of the cylinder = πr2h
= (3.14 × 32 × 5)
= 141.3 cm3
Hence, the volume of the cylinder is 141.3 cm3
问题5.高度为1 m的密闭圆柱形容器的容量为15.4升。制作它需要多少平方米的金属板?
解决方案:
Given that,
The height of the cylindrical vessel = 1m
The capacity/volume of the cylinder = 15.4 liters = 0.0154 m3 (As we know 1m3 = 1000 liter)
Let’s assume that the radius of the circular ends of the cylinders be ‘r’
So the volume of the cylinder is
V = πr2h
0.0154 = (31.4)r2(1)
r = 0.07 m
Now we find the total surface area of a vessel:
TSA = 2πr(r + h)
= 2(3.14 x (0.07) x (0.07 + 1)) = 0.4703 m2
Hence, we need 0.4703 m2 of the metal sheet
问题6.医院的病人每天在直径7厘米的圆柱形碗中喝汤。如果碗中盛有高至4厘米的汤,医院每天必须准备多少汤才能为250名患者提供服务?
解决方案:
Given that,
The diameter of cylindrical bowl = 7 cm = 3.5 cm
So, the radius = 7/2 cm = 3.5 cm
The bowl is filled with soup to a height =4cm
Now we find the volume soup in 1 bowl
V = πr2h
= 22/7 × 3.52 × 4 = 154 cm3
So the volume soup in 250 bowl
V = (250 × 154) = 38500 cm3 = 38.5 liter
Hence, the soup, hospital has to prepare daily to serve 250 patients is 38.5 liter.
问题7.一个空心的花园滚子,宽63厘米,周长440厘米,由4厘米厚的铁制成。找到铁的体积。
解决方案:
Given that,
Garden roller height = 63 cm,
Garden roller outer circumference = 440 cm,
Garden roller thickness = 4 cm
Find the volume of iron.
So, let’s assume that the R be the external radius and the inner radius be ‘r’
2πR = 440
2 x 22/7 x R = 440
R = 70
Now we find the value of inner radius:
r = R – 4
70 – 4 = 66cm
Now we find the volume of the iron:
V = π (R2 − r2) x h
= 22/7 x (702 − 662) x 63
= 22/7 x 4 x 136 x 63 = 107712 cm3
Hence, the volume of the iron is 107712 cm3
问题8.实心圆柱体的总表面积为231cm 2 。其弯曲的表面积为总表面积的2/3。找到圆柱体的体积。
解决方案:
Given that,
Total surface area = 231cm2,
Curved surface area = 2/3 x (Total Surface Area)
So,
Curved surface area = 2/3 x 231 = 154
As we know that,
the total surface area of cylinder = 2πrh + 2πr2
2πrh + 2πr2 = 231 —————-(i)
Where, 2πrh is the curved surface area, So
154 + 2πr2 = 231
2πr2 = 231 – 154
2πr2 = 77
2 x 22/7 x r2 = 77
r2 = (7×7) / (2×2)
r = 7/2
The radius of cylinder = 7/2
Now we find the height of the cylinder
So, as we know that
Curved surface area = 2πrh
2πrh = 154
2 x 22/7 x 7/2 x h = 154
h = 154/22 = 7
So, the height of cylinder = 7
Now we find the volume of the cylinder:
Volume = πr2h
= 22/7 x 7/2 x 7/2 x 7 = 269.5 cm3
So, the volume of the cylinder is 269.5 cm3
问题9:在一个封闭的圆柱形油箱的总外表面上以每平方分米50帕的涂漆成本为198卢比。油箱的高度是油箱底部半径的6倍。找到校正到小数点后两位的音量。
解决方案:
Let’s assume that the radius of the tank = r dm
So, the height of the tank(h) = 6r dm
It is given that the cost of painting = 50 paisa per dm2
So, the total cost of painting = Rs 198
= 2πr(r + h) = 198
= 2 × 22/7 × r(r + 6r) × 1/2 = 198
r = 3 dm
Hence the radius of the tank is 3 dm
Therefore, h = (6 × 3) dm = 18 dm
As we know that,
Volume of the tank = πr2h
= 22/7 × 9 × 18 = 509.14 dm3
问题10:两个圆柱体的半径之比为2:3,其高度之比为5:3。计算它们的体积比和它们的曲面比。
解决方案:
Given that the ratio of the radii of two cylinders = 2:3
The ratio of the heights two cylinders = 5:3
So, let’s assume that the radius of the two cylinders are 2x and 3x
The height of the two cylinders is 5y and 3y
Find: The ratio of their volumes and the ratio of their curved surfaces
So, for the ratio of their volumes:
We have
Volume of cylinder A/ Volume of cylinder B = π (r)2 h/π (R)2 H
= π (2x)2 5y/π (3x)2 3y = 20/27
Hence, the ratio of the volumes of two cylinders are 20:27.
So, for the ratio of their surface area:
We have
Surface area of cylinder A / Surface area of cylinder B = 2πrh/2πRH
= (2π × 2x × 5y) / (2π × 3x × 3y) = 10 / 9
Hence, the ratio of the surface area of two cylinders are 10:9.
问题11.直角圆柱体的曲面表面积与总表面积之比为1:2。如果圆柱体的总表面积为616 cm 2 ,则求出圆柱体的体积。
解决方案:
Given that
Total surface area (TSA) = 616 cm2
The ratio between the curved surface area and the total surface area of a right circular cylinder = 1 : 2
Find: the volume of the cylinder
According to the question
Curved Surface Area / Total Surface Area = 1/2
CSA = 1/2 x TSA
CSA = 1/2 x 616
CSA = 308 cm2
Now, we find the total surface area
TSA = 2πrh + 2πr2
616 = CSA + 2πr2
616 = 308 + 2πr2
2πr2 = 616 – 308
2πr2 = 308
πr2 = 308/2
r2 = 308/2π
r = 7 cm
Since, CSA = 308 cm2
2πrh = 308
2 x 22/7 x 7 x h = 308
h = 7cm
Now we find the volume of cylinder
V = πr2 x h
= 22/7 x 7 x 7 x 7
= 22 x 49
= 1078 cm3
Hence, the volume of cylinder is 1078 cm3
问题12.圆柱体的曲面面积为1320 cm 2 ,其底部直径为21 cm。找到圆柱体的高度和体积。
解决方案:
Given that
The curved surface area of a cylinder = 1320 cm2
Diameter of its base = 21 cm
So, radius = 21/2 = 10.5 cm
r = 21/2 = 10.5 cm
Find: the height and volume of the cylinder.
So, the curved surface area of a cylinder is
CSA = 2πrh
2 x 22/7 x 10.5 x h = 1320
h = 1320/66 = 20 cm
So the height of the cylinder is 20 cm
Now we find the volume of cylinder
V = πr2 h
= 22/7 x 10.5 x 10.5 x 20
= 22 x 1.5 x 10.5 x 20 = 6930 cm3
Hence, the volume of cylinder is 6930 cm3
问题13:底座的半径与圆柱体的高度之比为2:3。如果圆柱体的体积为1617 cm 3 ,则找到圆柱体的总表面积。
解决方案:
Given that,
The volume of the cylinder = 1617 cm3
The ratio between the radius of the base and the height of a cylinder = 2:3
r/h = 2/3
r = 2/3 x h ——————–(i)
Find: The total surface area of the cylinder
So, we find the volume of cylinder
V = πr2 h
1617 = 22/7 x (2/3 x h)2 x h
1617 = 22/7 x (2/3 x h)3
h3 = (1617 x 7 x 3) / 22 x 4
h = 10.5 cm
From, eqn. (i), we get
r = 2/3 x 10.5 = 7 cm
Now we find the total surface area of cylinder
TSA = 2πr (h + r)
= 2 x 22/7 x 7(10.5 + 7)
= 44 x 17.5
= 770 cm2
Hence, the total surface area of cylinder is 770 cm2
问题14.将一张44厘米x 20厘米的矩形纸沿着其形状圆柱体的长度滚动。查找如此形成的圆柱体的体积。
解决方案:
Given that,
The dimensions of the rectangular sheet of paper = 44 cm x 20 cm
So,
Length = 44 cm,
Height = 20 cm
Find: The volume of the cylinder
Curved Surface Area = 2πr
2πr = 44
r = 44/2π
r = 44/2π = 7 cm
Hence, the radius of the cylinder is 7 cm
Now, we find the volume of cylinder
V = πr2 h
= 22/7 x 7 x 7 x 20
= 154 x 20 = 3080 cm3
Volume of cylinder is 3080 cm3
问题15.圆柱柱的弯曲表面积为264 m 2 ,其体积为924 m 3 。找到支柱的直径和高度。
解决方案:
Given that,
The curved surface area of the cylindrical pillar = 264 m2
The volume of the cylindrical pillar = 924 m3
We have to find the diameter and the height of the pillar
So,
Volume of the cylinder
V = πr2h
π x r2 x h = 924
πrh(r) = 924
πrh = 924/r
As we know that the curved surface area of the cylinder
CSA = 2πrh
264 = 2πrh …(1)
Substitute πrh in this eq and we get,
2 x 924/r = 264
r = 1848/264 = 7 m
Substitute r value in eq (i) and we get,
2 x 22/7 x 7 x h = 264
h = 264/44 = 6 m
Hence, the diameter = 2r = 2(7) = 14 m and height = 6 m
问题16:两个等体积的圆柱体的高度比例为1:2。找到两个半径的比例。
解决方案:
Let’s assume that we have two cylinders,
So, the radius of the cylinders = r1, r2
The height of the cylinders = h1, h2
The volume of the cylinders = v1, v2
According to the question
It is given that the h1/h2 = 1/2 and v1 = v2
We have to find the ratio of two radii
So,
v1/v2 = (r1/r2)2 x (h1/h2)
As v1 = v2
v1/v1 = (r1/r2)2 x (1/2)
1 = (r1/r2)2 x (1/2)
(r1/r2)2 = (2/1)
(r1/r2) = √2 / 1
Hence, the ratio of the radii are √2:1