halloo tolong bantu aku dong

Hai! ^_^ Iya, ini aku bantu:

25.
r = 1/2 × d
r = 1/2 × 28 cm
r = 14 cm

L = 1/2 × π × r²
= 1/2 × 22/7 × (14 cm)²
= 1/2 × 22/7 × 196 cm²
= 22/14 × 196 cm²
= 308 cm²

26.
s = r
s = 14 cm

d = 2r
d = 2 × 14 cm
d = 28 cm

K gabungan = K₁ + K₂
K gabungan = (3/4 × π × d) + (1/2 × 4s)
= (3/4 × 22/7 × 28 cm) + (1/2 × 4 × 14 cm)
= (66/28 × 28 cm) + 28 cm
= 66 cm + 28 cm
= 94 cm

^_^ ^_^