Afla valoarea numarului necunoscut din urmatoarele expresii: f. 402+[1002:3-(100+a)x2]:14=408 g. 40+90:[9+48:(a+6)]=46 h. [(38xa+120):25x54]-980=100 i. 7777-(77:7+a-7777:7+777)x7=777 j. [80x(a:16-64)x60-3980]:4=3805
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Răspuns:
Explicație pas cu pas:
f).
402+[1002:3-(100+a)x2]:14=408
[334 - ( 100 + a ) × 2] : 14 = 408 - 402
[334 - ( 100 + a ) × 2] : 14 = 6
334 - ( 100 + a ) × 2 = 6 × 14
334 - ( 100 + a ) × 2 = 84
( 100 + a ) × 2 = 334 - 84
( 100 + a ) × 2 = 250
100 + a = 250 : 2
100 + a = 125
a = 125 - 100
a = 25
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g).
40+90:[9+48:(a+6)]=46
90 : [9 + 48 : ( a + 6 )] = 46 - 40
90 : [9 + 48 : ( a + 6 )] = 6
9 + 48 : ( a + 6 ) = 90 : 6
9 + 48 : ( a + 6 ) = 15
48 : ( a + 6 ) = 15 - 9
48 : ( a + 6 ) = 6
a + 6 = 48 : 6
a + 6 = 8
a = 8 - 6
a = 2
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h).
[(38xa+120):25x54]-980=100
[(38 × a + 120) : 25 × 54] = 100 + 980
[(38 × a + 120) : 25 × 54] = 1 080
(38 × a + 120) : 25 = 1 080 : 54
(38 × a + 120) : 25 = 20
38 × a + 120 = 20 × 25
38 × a + 120 = 500
38 × a = 500 - 120
38 × a = 380
a = 380 : 38
a = 10
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i).
7 777 - (77 : 7 + a - 7 777 : 7 + 777) x 7 = 777
(11 + a - 1 111 + 777) × 7 =7 777 - 777
(11 + a - 1 111 + 777) × 7 = 7 000
11 + a - 1 111 + 777= 7 000 : 7
11 + a - 1 111 + 777 = 1 000
11 + a = 1 000 - 777 + 1 111 → aplic metoda mersului invers
11 + a = 223 + 1 111
11 + a = 1 334
a = 1 334 - 11
a = 1 323
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j).
[80 × (a : 16 - 64) × 60 - 3 980] : 4 = 3 805
80 × (a : 16 - 64) × 60 - 3 980 = 3 805 × 4
80 × (a : 16 - 64) × 60 - 3 980 = 15 220
80 × (a : 16 - 64) × 60 = 15 220 + 3 980
80 × (a : 16 - 64) × 60 = 19 200
a : 16 - 64 = 19 200 : 60 : 80
a : 16 - 64 = 320 : 80
a : 16 - 64 = 4
a : 16 = 4 + 64
a : 16 = 68
a = 68 × 16
a = 1 088