Question

Va rog ajutatima la aceste probleme !
1. Un obiect costa 100 lei. Se scumpeste 3 saptamani consecutive cu cate 20%.Aflati pretul final.

2. 3 numere sunt invers proportionale cu 2;3;4 si suma lor este 80.Aflati numerele.

3. la un test clasa obtine 4 note de 3 , 5 note de 4 , 6 note de 6 , 3 note de 7 , 5 note de 10. Care este media clasei .

Answer 1

1. sapt 1> 100+20/100*100=120
sapt 2> 120+120*20/100=120+24=144
sapt 3> 144+144*20/100=144+28.8=172.8
2.
a+b+c=80
2a=3b=4c=k
2a=k , a=1/2k
3b=k, b=1/3 k
4c=k. c=1/4k
1/2k+1/3k+1/4k=80(aduc la acelasi numitor 12)
(6k+4k+3k)/12=80

6k+4k+3k=12*80
13k=12*80
k=96/13
a=96/13*1/2=48/13
b=96/13*1/3=32/13
c=96/13*1/4=24/13
3. ma=(4*3+5*4+6*6+3*7+5*10)/(4+5+6+3+5)=(12+20+36+21+50)/23=6.04