Question

Dau 30 puncte pt. ex. 18 si 19 + coronita.

Answer 1

18:diametru=48=2R
=> R=24 cm =0,24 m
L cerc=2*0,24π
L cerc=0,48π=1,5m - o rotatie completa
1,5*300=450 m
19:
a)L=2πR=> R=9
=> A=πR²=81πcm ²
b)L=4√3π=> R=2√3
=> A=12πcm²

Answer 2

18. Circumferinta cercului: 2×pi×r=d×pi=48cm×3,14=150,72cm;
Cati metri a parcurs bicicleta?
150,72cm×300=45215cm=452,15m ;
19.
a)18pi=2×pi×r |:(2×pi);
r=9(cm);
A=pi×r²=pi×9²=81pi(cm²);
b) 4¬/3 pi=2×pi×r |:(2×pi);
r= 2¬/3cm;
A=pi×r²=pi×(2¬/3)²=12pi(cm²)