Odpowiedź:
17.) a) [tex]\frac{3}{4}[/tex] tej liczby to 15 = 75% tej liczby to 15
100% = x (Mnożymy na ukos:)
75x = 1500
x = 20
b) [tex]\frac{8}{9}[/tex] tej liczby to 3[tex]\frac{1}{5}[/tex]
[tex]\frac{8}{9}[/tex] liczby x = [tex]\frac{16}{5}[/tex]
Całość tej liczby = x
[tex]\frac{8}{9}[/tex]x = [tex]\frac{16}{5}[/tex] I×9
8x = [tex]\frac{144}{5}[/tex] I:8
x = [tex]\frac{144}{40}[/tex] = [tex]\frac{72}{20}[/tex] = [tex]\frac{36}{10}[/tex] = [tex]\frac{18}{5}[/tex] = 3[tex]\frac{3}{5}[/tex]
c) 1[tex]\frac{2}{3}[/tex] tej liczby to 3[tex]\frac{3}{4}[/tex]
[tex]\frac{5}{3}[/tex] tej liczby = [tex]\frac{15}{4}[/tex]
Całość tej liczby = x
[tex]\frac{5}{3}[/tex]x = [tex]\frac{15}{4}[/tex] I×3
5x = [tex]\frac{45}{4}[/tex] I:5
x = [tex]\frac{45}{20}[/tex] = [tex]\frac{9}{4}[/tex] = 2[tex]\frac{1}{4}[/tex]
