Question

Va rog frumos!!!!!
Dupa ce a cheltuit it in prima zi 0,6 din suma,in a doua zi 1/3 din ceea ce ia ramas,Ana mai poate cheltui 48 de lei.Ce suma a avut initial?
Rezolvare pe scurt!!

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Answer 1

suma initiala: a

in prima zi a cheltuit: S1=0.6·a=6a/10=3a/5

a doua zi a cheltuit: S2=1/3(a-S1)=a/3-1/3·3a/5=a/3-a/5=2a/15

rest: 48=a-S1-S2 ⇔ 48 =a-3a/5-2a/15 ⇔ 48=a·(15-9-2)/15 ⇔48=4a/15 ⇒a=48·15/4=180 lei