mencari diameter lingkaran yang luasnya 1,54dm2

L = nr2
1,54 = 22/7 r2
r2 = 1,54 x 7/22
r2 = 0.49
r = 0,7 dm

d = 0,14 dm

Luas lingkaran = phi.r²
1,54 dm² = 22/7.r²
1,54.7/22 = r²
r² = 0,49 dm²
r² = 49 cm²
r = √49
r = 7cm = 0,7 dm
diameter = 14 cm = 1,4 dm