Question

Stiind ca:

a) b+c=21 si a=7 , calculati a x b +a x b
b) b-c=31 si a x b -a x c =837,calculati a
c)a x b- a x c =1440 si a=45,calculati b-c
d)a+b -c=48 si d=144 : (95-83),calculati a x d = b x d -c x d
e)b-c=7,a=14,b=21,calculati a x (b-c) +a x b

Answer 1

a)  b + c = 21  si a = 7

 a × b + a × c = a × ( b + c ) = 7 × 21 = 147

b)  b - c = 31

a × b - a × c = 837

a × ( b - c ) = 837

a × 31 = 837

a = 837 : 31

a = 27

c)   a = 45

a × b - a × c = 1 440

a × ( b - c ) = 1 440

45 × ( b - c ) = 1 440

b - c = 1 440 : 45

b - c = 32

d)

a + b - c = 48   si   d = 144 : 12 ⇒  d = 12

a × d + b × d - c × d =

= d × ( a + b - c ) =

= 12 × 48 =

= 576

e)

b - c = 7;   a = 14;  b = 21

a × ( b - c ) + a × b =

= 14 × 7 + 14 × 21

= 14 × ( 7 + 21 )

= 14 × 28 =

= 392