9 ampe 10 ya kak .. Tolong dijawab pake caraa.. Makasihh

no 9. Luas = πr^2
Luas = 22/7 x 21 x 21
Luas = 22 x 3 x 21
Luas = 1386 m^2

no 10. Luas = πr^2
1.54 = 22/7 r^2
1.54 x 7 /22 = r^2
0.49 = r^2
r = 0.7 dm
r = 7 cm
d = 14 cm