Question

Intr-o saptamana,radu a citit 161 pagini.In fiecare zi a citit cu o pagina mai mult fata de ziua precedenta.Cate pagini a citit in ultima zi?

Answer 1

$x \to cat \ a \ citit \ intr-o \ zi \\\\\\ x+(x+1)+(x+2)+(x+3)+(x+4)+(x+5)+(x+6)=161 \\\\ 7x+1+2+3+4+5+6=161 \\\\ 7x+21=161 \\\\ 7x=161-21 \\\\ 7x=140 \ \ |:7 \\\\ \boxed{x=20 \ pagini \ a \ citit \ in \prima \ zi} \\\\\\ \hbox{In ultima zi Radu a citit x+6 pagini ceea ce inseamna ca a citit:} \\\\ 20+6 \to \boxed{26 \ pagini \ a \ citit \ ultima \ zi}$

Answer 2

1 |-----|
2 |-----|+1|
3 |-----|+1|+1|
4 |-----|+1|+1|+1|
5 |-----|+1|+1|+1|+1|
6 |-----|+1|+1|+1|+1|+1|
7 |-----|+1|+1|+1|+1|+1|+1|               } 161.

161 - 21 = 140   ( 7 segmente egale)
140 : 7 = 20 pagini (1 zi)
20 +1 = 21 pagini ( 2 zi )
20 +1+1 = 22 pagini ( 3 zi)
20 +1+1+1 = 23 pagini ( 4 zi )
20 +1+1+1+1 = 24 pagini ( 5 zi )
20 +1+1+1+1+1 = 25 pagini ( 6 zi )
20 +1+1+1+1+1+1 = 26 pagini ( 7 zi)
Verificare : 20 + 21 + 22 + 23 + 24 + 25 + 26 =161.