Question

Cum fac diferenta intre marimi direct proportionale si marimi invers proportionale?

Answer 1

La direct proportional:

Scade o marime, scade si cealalta.

Creste oo marime,  creste si cealalta.

De exemplu: Un kilogram de mere costa 3lei

1 kg => 3lei

2kg => 6lei

0,5kg => 1,5lei

1kg....................3lei

2kg..................x lei

______________

1/2=3/x ⇒ x=2·3=6

La invers proportional:

Creste o marime, scade cealalta

Scade o marime, creste cealalta

De exemplu: Doi munctiori termina o lucrare in 4 zile

Deci un muncitor termina lucrarea in 8 zile

(Lucreaza singur, deci mai incet)

Dar 4 muncitori termina lucrarea in 2 zile

(Lucreaza mult mai repede)

1 muncitor...........................8 zile

4 muncitori.........................x zile

_______________________i.p.

1·8=4·x ⇒ x=8:4=2 (zile)

sau 1/x=4/8