okay... i'm translating this from japanese to english, so i dunno how much you're gonna understand... but plz try...
There is a two-digit number. The sum of the tenth number (the one on the left... like in 10 it is 1) and the ones number (like in 10 it is 0) is 9. The tenth number is 1 more than 3 times the ones number.
What are the two numbers in the number?
2006-11-12 13:38:42 · 5 answers · asked by Seira T 1 in Science & Mathematics ➔ Mathematics
This is solvable, and you wrote it very well!
The key to setting this up is knowing that for any 2-digit number, you can write it as 10a + b.
So your problem states that a+b=9 (the sum of the tens digit and ones digit is 9), and it states that a=3b+1 (the tens digit is 1 more than 3 times the ones digit).
So now you have 2 equations in 2 unknowns, which you can easily solve for:
a + b = 9
a = 3b + 1
Substitute a = 3b + 1 into the first equation to get:
a + b = 9
(3b + 1) + b = 9
4b + 1 = 9
4b = 8
b = 2
Now you can easily solve for a, which equals 7 since a+b=9.
So your 2-digit number is 72.
Check: 7+2=9
7 = 1 + 3*2
It checks out, so our answer is correct!
~ ♥ ~
2006-11-12 13:41:41 · answer #1 · answered by I ♥ AUG 6 · 0⤊ 0⤋
Assume the number you are ultimately looking for is xy.
Then x+y = 9 and
x=1+3y
replace 'x' in the first equation and you get:
(1+3y) + y = 9
1+4y=9
1+4y-1=9-1
4y=8
y=2
Then put that back in the first equation and you get:
x+2=9
x+2-2=9-2
x=7
so your final number is
72
2006-11-12 21:45:48 · answer #2 · answered by Heather M 2 · 0⤊ 0⤋
72
2006-11-12 21:45:57 · answer #3 · answered by tamana 3 · 0⤊ 0⤋
x + y = 9
3x + 1 = y
-3x - 3y = -27
3x + 1 = y
1 - 3y = y - 27
4y = 28
y = 7
3x + 1 = 7
3x = 6
x = 2
72
2006-11-12 21:45:29 · answer #4 · answered by bourqueno77 4 · 0⤊ 0⤋
i think its 72...not sure
2006-11-12 21:45:06 · answer #5 · answered by Anonymous · 0⤊ 1⤋