數學16題(超急)要詳細計算(只做A)

5(a) A=(5×8÷2)-(3×4÷2)=20-6=14cm²
5(b) A=(6×8÷2)-[(3+8)×2÷2]=24-11=13cm²

6(a) A=[(3.5+6.5)×4÷2]-(3×4÷2)=20-6=14cm²
6(b) A=[(10+20)×16÷2]-(8×20÷2)=240-80=160cm²

7(a) A=(5×4)-(4×2)=20-8=12cm²
7(b) A=(12×8)-(12×5÷2)=96-30=66cm²

8(a) A=(12×12)-[(7×8)+(4×12)+(5×12)]÷2=144-82=62cm²
8(b) A=(10×6)-[(10×3)+(4×6)+(6×3)]÷2=60-36=24cm²

9(a) x=66÷6=11cm
9(b) x=2×45.5÷7=13cm

10(a) x=2×168÷(10+18)=12cm
10(b) x=2×56÷7-6=10cm

11(a) x=9×8÷15=4.8cm
11(b) x=9÷15×12=7.2cm

12(a) x=8×12÷6=16cm
12(b) x=6×10÷12=5cm

13(a) A=(12×4)+[(2+4)×2÷2]-(2×2÷2)=48+6-1=53cm²
13(b) A=[(2+3)×3÷2]+[(3+5)×4÷2]-(1×1)=7.5+16-1=22.5cm²

14(a) A=(8×5÷2)+(8×4÷2)-(8×3÷2)=20+16-12=24cm²
14(b) A=(11×8÷2)+(12×10÷2)-(7×3÷2)=44+60-10.5=93.5cm²

15(a) A=(3.5×5)-{(0.8×0.5)+(1×1)+[(0.5+2)×1÷2]}=17.5-(0.4+1+1.25)=14.85m²
15(b) 14.85÷27=0.55L

16
　　
圖片參考：http://i1233.photobucket.com/albums/ff384/oldmanjdd/Maths/cut.jpg?t=1298264503

我唔識打次方符號… = =
以下用 *代表乘; ^2 代表 2次方



5.(a) 著色部份面積
= 5*8/2 - 3*4/2
= 14 cm^2
6.(a) 著色部份面積
= (3.5 + 6.5)*4/2 - 3*4/2
= 14cm^2
7.(a) 著色部份面積
= 5*4 - 2*4
= 12 cm^2
8.(a) 著色部份面積
= 12*12 - 4*12/2 - 5*12/2 - (12-4)(12-5)/2
= 62 cm^2

9.(a) 6x = 66
x = 11
10.(a) (10+18)x = 168
x = 6
11.(a) 15x/2 = 8*9/2
x = 4.8
12.(a) 6x = 8*12
x = 16

13.(a) 著色部份面積
= (2 + 4)*2/2 + (4 + 4 + 4)*4 - [(4 + 4 + 4 - 5 - 5)*2/2]
= 6 + 48 - 2
= 52 cm^2
14.(a) 著色部份面積
= 5*8/2 + 4*8/2 - 3*8/2
= 24 cm^2

15.(a) 需髹上油漆的牆壁的面積
= 5*3.5 - 0.8*0.5 - 1*1 - [(1 + 0.5 + 0.5) + 0.5]*1/2
= 14.85 m^2

16

圖片參考：http://imgcld.yimg.com/8/n/HA05426997/o/701102200095913873382520.jpg


2011-02-21 13:13:16 補充：
第10題寫錯0.0

(10+18)x/2 = 168
x = 12

5a. area of big triangle – area of small triangle
(5 X 8)/2 - (3X4)/2 = 20 – 6 = 14 sq. cm

6a area of trapezoid - . area of triangle
(6.5 + 3.5)X4/2 – 3X4/2 = 20 – 6 = 14 square cm

7a. area of parallelogram – area of rectangle
5 X 4 – 2 X 4 = 20 – 8 = 12 sq. cm

8a.. area of big square – area of 3 triangle
12 X 12 – (12X4/2 + 12 X5/2 + [(12-4)X(12 – 5)/2]
144 – (24 + 30 + 28) = 144 – 82 = 62 sq. cm

9a. area of parallelogram = base x height
66 = 6 X height
height = 66/6 = 11 cm
height is represented by x = 11 cm

10a. area of trapezoid = (top + bottom) x height/2
168 = (10 + 18) X height/2
168 = 28 X height/2
height = 168 X 2/28 = 12 cm
height is represented by x = 12 cm

11a. area of triangle where x is the height
8 X 9/2 = 15x/2
36 = 7.5x
x = 36/7.5 = 4.8 cm
x = 4.8 cm
area of triangle can be calculated from different base and height
One base is 15 cm, the other base is 9 cm

12a. area of parallelogram
12 X 8 = 6 x
x = 96/6
x = 16 cm

13 a. area of rectangle + area of trapezoid - area of triangle
12 x 4 +(2 +4)X2/2 – 2X2/2
48 + 6 – 2
52 sq. cm

14 a. 5 X 8/2 + 4 X8/2 – 3X8/3
20 + 16 – 12
24 sq. cm

15 a. area = 3.5 X 5 – 0.8 X0.5 – [(0.5 + 2)X1/2 + 1X1]
area = 17.5 -0.4 – [1.25 + 1]
area = 14.85 sq m

16. There is no part (a)


2011-02-21 13:09:16 補充：
Correction:
14 a. 5 X 8/2 + 4 X8/2 – 3X8/2

too many questions ~ run out of space for detailed steps !!

2011-02-21 13:27:55 補充：
To Pak Wai :

No offence
For question 10 a
You forget to divide by 2 for area of trapezoid
area = (top + bottom) x height/2