tim 1 số có 2 chữ số biết rằng khi viết thêm chữ số 9 vào bên trái chữ số đó ta được 1 số gấp 13 lần số phải tìm
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Những câu hỏi liên quan
NM
Nguyễn Minh Quang
Giáo viên
7 tháng 3 2021
1. khi thêm 4 vào bên trái số đó nghĩa là ta đã cộng thêm với 400
ta được số mới gấp 9 lần số ban đầu
nên 400 gấp 8 lần số ban đầu
hay số ban đầu là \(400:8=50\)
2. khi thêm 9 vào bên trái số đó nghĩa là ta đã cộng thêm với 900
ta được số mới gấp 13 lần số ban đầu
nên 900 gấp 12 lần số ban đầu
hay số ban đầu là \(900:12=75\)
HH
20 tháng 9 2014
Gọi số phải tìm là ab. Viết thêm chữ số 4 vào bên trái ta dược số 4ab. Theo bài ra ta có:
94ab = ab x 9
400 + ab = ab x 9
400 = ab x 9 – ab
400 = ab x (9 – 1)
400 = ab x 8
ab = 400: 8
ab = 50
20 tháng 7 2015
gọi số đó là abcd
abcd5=5x1abcd
abcdx10+5=50000+abcdx5
suy ra abcdx5=49995
nên abcd=49995:5
abcd=9999
vậy số đó là 9999
26 tháng 8 2021
1,Gọi số cần tìm là ab
Khi viết thêm chữ số 9 vào bên trái ta có : 9ab
Theo bài ra ta có :
ab x 13 = 9ab
ab x 13 = 900 + ab
ab x 13 - ab =900
ab x ( 13 - 1 ) = 900
ab x 12 = 900
ab = 900 : 12
ab = 75
2, Nếu viết thêm chữ số 5 vào bên phải thì số đó sẽ tăng 10 lần và 5 đơn vị
( bạn tự vẽ sơ đồ )
Số cần tìm là : ( 1112 - 5 ) : (10 - 1 ) = 123
23 tháng 8 2015
Gọi số phải tìm là A. Nếu viết thêm chữ số 4 vào bên trái ta dược số 4A.Theo bài ra ta có:
94A = A x 9
400 + A = A x 9
400 = A x 9 – A
400 = A x (9 – 1)
400 = A x 8
A= 400: 8
A = 50
13 tháng 4 2016
Bai giai
goi so can tim la ab (a>0)
Khi viet them chu so 4 vao ben trai so can tim ta duoc mot so gap chin lan so phai tim( 9ab) va so do chia het cho 9. Neu a= 1;b= 4 -> 414 a= 2;b= 3 -> 423 a= 3;b= 2 -> 432 a= 4;b= 1 -> 441 a= 5;b= 0 -> 450 a= 6;b= 8 -> 468 a=7;b= 7 -> 477 a=8;b=6 -> 486 a=9;b=6 -> 496 Ta thay a=5;b=0 thi thoa man, vay so can tim la 50 bai nay dung day co giao minh giang bai nay ma
2 tháng 5 2015
Gọi 3 số là abc
theo đb ta có
abc1=3 x 2abc
abc x 10 +1 =3x 2000+3abc
7 abc= 5999
abc=857
vậy số đó là 857
20 tháng 10 2018
857 dung 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10 tháng 12 2021
\(1,\Rightarrow\overline{7ab}=36\cdot\overline{ab}\Rightarrow\overline{ab}+700=36\cdot\overline{ab}\\ \Rightarrow35\cdot\overline{ab}=700\Rightarrow\overline{ab}=20\\ 2,\Rightarrow\overline{30abc}=151\cdot\overline{abc}\Rightarrow\overline{abc}+30000=151\cdot\overline{abc}\\ \Rightarrow\overline{abc}\cdot150=30000\Rightarrow\overline{abc}=200\\ 3,\Rightarrow\overline{ab5}=10\cdot\overline{ab}+5=554+\overline{ab}\\ \Rightarrow\overline{ab}\cdot9=549\Rightarrow\overline{ab}=61\\ 4,\Rightarrow\overline{ab78}=\overline{ab}\cdot100+78=1266+\overline{ab}\\ \Rightarrow\overline{ab}\cdot99=1188\Rightarrow\overline{ab}=12\\ 5,\Rightarrow\overline{abc85}=\overline{abc}\cdot100+85=43348+\overline{abc}\\ \Rightarrow\overline{abc}\cdot99=43263\Rightarrow\overline{abc}=437\\ 6,7,\text{Đề thiếu}\)
10 tháng 7 2015
a, Gọi số đó là ab(có gạch trên đầu) đk ab thuộc N
Theo đề bài ta có
9ab=ab.13
900+10a+b=(10a+b).13
900+10a+b=130a+13b
900=120a+12b
Ta có a=7 vì a<7 thì 12b=180 vậy b=15 ko thỏa mãn a=8,9 cũng ko thỏa mãn
từ đó 12b=900-840=60
Vậy b=60:12
b=5
Vậy số đó là 75
b Gọi số đó là abc(có gạch trên đầu) đk abc thuộc N và a,b,c thuộc N a khác 0
Nếu viết thêm chữ số 5 vào bên phải số đó thì tức là đã gấp số đó lên 10 lần và 5 đơn vị
9.abc=1112-5
9.abc=1107
Vậy abc=1107:9
abc=123 Vậy số đó là 123
12 tháng 10 2015
b) Gọi số cần tìm là abc
theo đề ta có abc5= abc+1112
=> abc.10+5=abc+1112
=> abc.9=1112-5
=> abc.9=1107
=> abc=1107chia 5
=> abc=123
Gọi số phải tìm là ab. Viết thêm chữ số 9 vào bên trái ta dược số 9ab. Theo bài ra ta có:
9ab = ab x 13
900 + ab = ab x 13
900 = ab x 13 – ab
900 = ab x (13 – 1)
900 = ab x 12
ab = 900: 12
ab = 75
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