Question

Un automobil a parcurs o distanta in trei zile astfel:in prima zi a parcus 7/20 din drum,a doua azi a parcurs 1/5 din distanta ramasa,iar a treia zi a parcurs restul de 624 km.
a)Cati km are intreaga distanta ?
b)Cati km a parcurs automobilul a doua zi ?

Answer 1

prima zi⇒7y/20;
a ramas y-7y/20=20y/20-7y/20=13y/20;
a doua zi⇒1/5 ·13y/20⇒13y/100;
a ramas 13y/20-13y/100=65/100-13/100=52y/100=26y/50=13y/25;
⇒13y/25=624⇒y=25·624/13⇒y=25·48⇒y=1200[km-intreaga distanta];
b. a doua zi⇒13·1200/100=13·12=156[km-a parcurs automobilul a doua zi];

Answer 2

distanta = D = prima zi + a doua zi + 624

in prima zi : a fost parcursa   D7/20         au ramas  = D- D7/20=  D* 13/20

a doua zi : 1/5   x 13D/20 =   13 D / 100

7D/20 + 13D/ 100 + 624 = D  ==>   D-7D/20 - 13D/100 = 624

(100D - 35D - 13D)/ 100 = 624 ==> D = 624 x100 : 52 = 1200 km

a doua zi = 1/5 x 13D/20 = 13 x 1200 /100 = 156 km