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
1.
Tìm một số có hai chữ số , biết rằng khi viết thêm chữ số 4 vào bên trái số đó ,ta được một số gấp 9 lần số phải tìm.
2.Tìm một số có 2 chữ số, khi viết thêm chữ số 9 vào bên trái số đó ta được một số gấp 13 lần số phải tìm .
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 \(900:12=75\)
tim 1 số có 2 chữ số biết rằng khi viết thêm chữ số 4 vào bên trái chữ số đó ta được 1 số gấp 9 lần số phải tìm
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
Tim số có 4 chữ số, biết rằng khi viết thêm chữ số 5 vào bên phải số đó ta được số lớn gấp 5 lần số nhận được khi ta viết thêm chữ số 1 vào bên trái số đó
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
gọi số đó là abcd
ta có
1abcd x 5 =abcd5
(10000+abcd).5=abcd.10+5
50000+5.abcd=10.abcd+5
5.abcd=50000-5
abcd=49995:5
abcd=9999
vậy số đó là : 9999
1:Tìm 1 số tự nhiên có hai chữ số ,biết rằng nếu viết thêm chữ số 9 vào bên trái số đó ta được một số lớn gấp 13 lần số đã cho.
2:Tìm 1 số có ba chữ số,biết rằng khi viết thêm chữ số 5 vào bên phải số đó thì nó tăng lên 1112 đơn vị
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
tim 1 số có hai chữ số ,biết rằng khi viết thêm chữ số 4 vào bên trái số đó ,ta được 1 số gấp 9 số phải tìm ?
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
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
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
Tìm 1 số có 2 chữ số , biết rằng khi viết thêm chữ số 4 vào bên trái số đó, ta được 1 số gấp 9 lần số phải tìm.
Gọi số cần tìm là ab ( 0 < a,b < 10 ) => Số mới là 4ab
Theo đề ra ta có :
4ab = ab x 9
400 + ab = ab x 9
400 = ab x 8
400 : 8 = ab
50 = ab
Vậy số cần tìm là 50
Thử lại : 450 : 50 = 9 (Đ)
Đáp số : 50
Khi viết thêm chữ số 4 vào bên trái số có 2 chữ số thì số đó tăng 400 đơn vị.
Số cần tìm là:
400 : ( 9 – 1 ) = 50
TL: 50 x 9 = 450 (Đ)
Vậy số đó là 50.
Tìm 1 số có 3 chữ số,biết rằng khi viết thêm chữ số 1 vào bên phải số đó thì ta được 1 số gấp 3 lần số có được bằng cách viết thêm chữ số 2 vào bên trái số đó
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
857 dung 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1. Tìm một số tự nhiên có 2 chữ số, biết rằng nếu thêm chữ số 7 vào bên trái số đó ta được một số lớn gấp 36 lần số đã cho.
2. Tìm một số có 3 chữ số, biết rằng khi viết thêm số 30 vào bên trái số đó ta được một số lớn gấp 151 lần số phải tìm.
3. Tìm một số có 2 chữ số, biết rằng khi viết thêm chữ số 5 vào bên phải số đó ta được số lớn hơn số phải tìm 554 đơn vị.
4. Tìm một số có 2 chữ số, biết rằng khi viết thêm số 78 vào bên phải số đó ta được số lớn hơn số phải tìm 1266 đơn vị.
5. Khi viết thêm số 85 vào bên phải một số tự nhiên có 3 chữ số thì số đó tăng thêm 43348 đơn vị. Tìm số có 3 chữ số đó.
6. Khi viết thêm số 65 vào bên phải một số tự nhiên thì số đó tăng thêm 78176 đơn vị. Tìm số đó.
7. Khi viết thêm số 56 vào bên phải một số tự nhiên thì số đó tăng thêm 122222 đơn vị. Tìm số đó.
\(1,\Rightarrow\overline{7ab}=36\cdot\overline{ab}\Rightarrow\overline{ab}+700=36\cdot\overline{ab}\\ \Rightarrow35\cdot\overline{ab}=700\Rightarrow\overline{ab}=20\\ 2,\Rightarrow\overline{30abc}=151\cdot\overline{abc}\Rightarrow\overline{abc}+30000=151\cdot\overline{abc}\\ \Rightarrow\overline{abc}\cdot150=30000\Rightarrow\overline{abc}=200\\ 3,\Rightarrow\overline{ab5}=10\cdot\overline{ab}+5=554+\overline{ab}\\ \Rightarrow\overline{ab}\cdot9=549\Rightarrow\overline{ab}=61\\ 4,\Rightarrow\overline{ab78}=\overline{ab}\cdot100+78=1266+\overline{ab}\\ \Rightarrow\overline{ab}\cdot99=1188\Rightarrow\overline{ab}=12\\ 5,\Rightarrow\overline{abc85}=\overline{abc}\cdot100+85=43348+\overline{abc}\\ \Rightarrow\overline{abc}\cdot99=43263\Rightarrow\overline{abc}=437\\ 6,7,\text{Đề thiếu}\)
a,Tìm 1 số tự nhiên có 2 chữ số,biết rằng nếu viết thêm chữ số 9 vào bên trái số đó ta được 1 số lớn gấp 13 lần số đã cho
b,Tìm 1 số tự nhiên có 3 chữ số ,biết rằng nếu viết thêm chữ số 5 vào bên phải số đó thì nó tăng thêm 1112 đơn vị
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
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
a.
Gọi số cần tìm là : ab
nếu viết thêm chữ số 9 vào bên trái ta được:9ab
hiệu của 9ab và ab là:
9ab-ab=900
ta có sơ đồ:
số ab: 1 ô
số 9ab: 13 ô(số 9ab lớn hơn ab là 900)
hiệu số phần bằng nhau:
13-1=12(phần)
số ab là:
900:12 nhân 1= 75
đáp số:75