Untuk Π=22/7 hitunglah diameter lingkaran yang luasnya: a.18.634 cm² b.308cm² c.1386cm²

a) Luas liangkaran = π r²
                   18.634 = 22/7 r²
                           r²  = 18.634 x 7/22
                               =  5929
                           r   = √5929
                               =  77
     diameter = 2 x r
                    = 2 x 77
                    = 154 cm
b) Luas lingkaran  = π r²
                    308   = 22/7 r²
                         r²  = 308 x 7/22
                             = 98
                         r  = √98
                            = 9,9 cm
 diameter = 19,8 cm
c) Luas lingkaran  =  π r²
                 1.386   = 22/7 r²
                         r²  = 1386 x 7/22
                             = 441
                         r   = √441
                             = 21 cm
 diameter = 42 cm
          

Penyelesaian:
Diket.:
π = 22/7
Ditanya:
a. d = ....?, jika L = 18.634 cm²
b. d = ....?, jika L = 308 cm²
c. d = ....?, jika L = 1.386 cm²
Jawab:
a.
Jika L = 18.634 cm², maka:
πr² = L
22/7 × r² = 18.634
r² = 18.634 : 22/7
r² = 18.634 × 7/22
r² = 130.438/22
r² = 5.929
r = √5.929
r = 77 cm

d = 2r
d = 2 × 77
d = 154 cm

b.
Jika L = 308 cm², maka:
πr² = L
22/7 × r² = 308
r² = 308 : 22/7
r² = 308 × 7/22
r² = 2.156/22
r² = 98
r = √98
r = √49×2
r = 7√2 cm

d = 2r
d = 2 × 7√2
d = 14√2 cm

c.
Jika L = 1.386 cm², maka:
πr² = L
22/7 × r² = 1.386
r² = 1.386 : 22/7
r² = 1.386 × 7/22
r² = 9.702/22
r² = 441
r = √441
r = 21 cm

d = 2r
d = 2 × 21
d = 42 cm

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