Question

Mai multi copii au o suma de bani. In prima zi cheltuiesc 20% din suma a doua zi 1/2 din rest si le mai raman 560 lei.
a) Cati lei au cheltuit a doua zi?
b) Cati lei au avut initial?

Answer 1

x-suma initiala
Z1=20℅×x
100℅-20℅=80℅
Z2=1/2×(80℅×x)
Z3=560
20℅×x+1/2×(80℅×x) +560=x
20/100×x+1/2×(80/100×x) +560=x
1/5x+1/2×4/5x +560=x
1/5x+2/5x+560=x
x+2x+2800/5=x
3x+2800=5x
3x-5x=-2800
-2x=-2800
x=-2800:(-2)
x=1400

Z1=20/100×1400=280
Z2= 1/2×(80/100×1400)= 1/2×1120=560