Jawabanmu

2014-06-10T20:06:40+07:00
L = π r ²
15400 = 22/7 × r²
15400 : 22/7 = r²
15400 × 7/22 = r²
  700  × 7      = r²
    4900         = r²
       r            = √4900 = 70 cm
2014-06-10T20:06:57+07:00
Πr² = 15400
22/7 r² = 15400
r² = 15400 x 7/22
r² = 4900
r = 70