Question

Dacă a=18 și b+c=57,calculați valoarea expresiilor.
a)a+5×b+5×c
b)3×a+2×b+2×c
c)a×b+a×c+7×c

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Answer 1

a+5×b+5×c=
18+5×57=
18+285=303

3×a+2×b+2×c=
3×18+2×57=
54+114=168

a×b+a×c+7×c=
a×(b+c)+c×(a+7)=
1026+c×25=
1026:25=41 rest 1

Answer 2

a = 18   si  b + c = 57

a)  

a + 5 × b + 5 × c = 303

18 + 5 × ( b + c ) =

= 18 + 5 × 57 =

= 18 + 285 =

= 303

_____________

b)

3 × a + 2 × b + 2 × c = 168

= 3 × 18 + 2 × ( b + c ) =

= 54 + 2 × 57 =

= 54 + 114 =

= 168

_________________

c) Corectie:  7 × a in loc de 7 × c

a × b + a × c + 7 × a = 1 152

= a × ( b + c + 7 ) =

= 18 × ( 57 + 7 ) =

= 18 × 64 =

= 1 152