Question

:P
tính diện tích hình tròn có bán kính r
a) r = 5cm      b)r = 9cm      c)r = 0,4      d)r = \(\dfrac{4}{9}\)
 

Answer 1

a: \(S=5\cdot5\cdot3.14=78.5\left(cm^2\right)\)

b: \(S=9\cdot9\cdot3.14=254.34\left(cm^2\right)\)

c: \(S=0.4^2\cdot3.14=0.5024\)

d: \(S=\left(\dfrac{4}{9}\right)^2\cdot3.14=\dfrac{1256}{2025}\)

Answer 2

a) \(R^2\times3,14=5^2\times3,14=78,5cm^2.\)

b) \(R^2\times3,14=9^2\times3,14=254,34cm^2.\)

c) \(R^2\times3,14=0,4^2\times3,14=0,5024cm^2.\)

d) \(R^2\times3,14=\left(\dfrac{4}{9}\right)^2\times3,14=\dfrac{1256}{2025}cm^2.\)

Answer 3

Diện tích hình tròn:

a) r x r x 3,14 = 5 x 5 x 3,14 = 78,5(cm²)

b) r x r x 3,14 = 9 x 9 x 3,14 = 254,34(cm²)

c) r x r x 3,14 = 0,4 x 0,4 x 3,14= 0,5024 (đvdt)

s) r x r x 3,14 = 4/9 x 4/9 x 3,14= 1256/2025(đvdt)

Answer 4

\(a,S:5\times5\times3,14=78,5\left(cm^2\right)\\ b,S:9\times9\times3,14=254,34\left(cm^2\right)\\ c,S:0,4\times0,4\times3,14=0,5024\\ d,\dfrac{4}{9}\times\dfrac{4}{9}\times3,14=\dfrac{16\times3,14}{81}=50,24\)

Answer 5

f

Answer 6

f

Answer 7

f

Answer 8

f

Answer 9

f

Answer 10

f

Answer 11

f

Answer 12

f

Answer 13

a) r x r x 3,14 = 5 x 5 x 3,14 = 78,5(cm²)

b) r x r x 3,14 = 9 x 9 x 3,14 = 254,34(cm²)

c) r x r x 3,14 = 0,4 x 0,4 x 3,14= 0,5024 (cm²)

s) r x r x 3,14 = 4/9 x 4/9 x 3,14= 1256/2025(cm²)