zad. 21
odp.: B
zad. 22
odp.: A
zad. 23
Pc = 2ab + 2bc + 2ac
Pc = 2 × 2 cm × 5 cm + 2 × 2 cm × 20 cm + 2 × 5 cm × 20 cm = 20 cm² + 80 cm² + 200 cm² = 300 cm²
zad. 24
Pc = 2Pp + Pb
Pb = 6 dm × 4 dm + 8 dm × 4 dm + 10 dm × 4 dm = 24 dm² + 32 dm² + 40 dm² = 96 dm²
Pp = (6 dm × 8 dm) : 2 = 24 dm²
Pc = 2 × 24 dm² + 96 dm² = 48 dm² + 96 dm² = 144 dm²
zad. 25
a) x - 13 = 28
x = 28 + 13
x = 41
spr.
P = 28
L = 41 - 13 = 28
P = L
b) 13 + x = 28
x = 28 - 13
x = 15
spr.
P = 28
L = 13 + 15 = 28
P = L
zad. 26
a) a + 17 = 54
a = 54 - 17
a = 37
b) 96 : b = 4
96 = 4 × b
96 : 4 = b
24 = b
b = 24
c) c - 6 = 27
c = 27 + 6
c = 33
d) d × 8 = 112
d = 112 : 8
d = 14
zad. 27
x - ołówek
x + 3 - długopis
2x + 2(x + 3) = 18
2x + 2x + 6 = 18
4x = 18 - 6
4x = 12
x = 3
odp.: Ołówek kosztował 3 zł.
zad. 28
a) P = a × h
P = 6 cm × 3 cm = 18 cm²
b) P = (e × f) : 2
P = (4 cm × 10 cm) : 2 = 20 cm²
c) P = [(a + b) × h] : 2
P = [(5 cm + 6 cm) × 4 cm] : 2 = (11 cm × 4 cm) : 2 = 22 cm²
