1. SUma masurile unghiurilor unu paralelipiped convex = 360°
a, b, c, d - unghiuri
a + b + c + d = 360
a, b ,c, d sunt proportionale cu nr 3, 4, 5 si respectiv 6.
a = 3k ; b = 4k ; c = 5k ; d = 6k
3k + 4k + 5k + 6k = 360⇒18k = 360⇒k = 20
a = 3k =60° ; b = 4k = 4 ×20 = 80° ; c = 5k = 5 × 20 =100° ; d = 6k= 6 ×20 = 120°
2)
0,(3)=3/9=1/3 ;0,25=25/100=1/4 ; 0,125=125/1000=1/8; 0,(1)=1/9
{a , b, c, d} d.p. { 1/3; 1/4 ; 1/8; 1/9)
a = 3k ; b = 4k ; c = 8k; d = 9k
a + b + c + d = 360
3k + 4k + 8k + 9k = 360
24k = 360
k = 360 : 24
k = 15
a = 3k= 3×15 = 45° ; b = 4k= 4× 15 = 60° ; c = 8k= 8 × 15° = 120°; d = 9k = 9 × 15 = 135°
