the sum of the digits of a two-digit number is 9. if the number is doubled, then decreased by 36, the answer is the orginal number reversed. find the number..
2007-10-16 17:21:44 · 5 answers · asked by Anonymous in Education & Reference ➔ Homework Help
it has to be an equation.. i can do it trial and error and not i need an equation..
2007-10-16 17:28:31 · update #1
Let x and y be the digits of the number.
x + y = 9
2(10x + y) - 36 = 10y + x
20x + 2y - 36 = 10y + x
19x - 8y - 36 = 0
19x - 8y = 36
Rewrite the original:
x = 9 -y
19(9 - y) - 8y = 36
171 - 19y - 8y = 36
171 - 27y = 36
135 = 27y
y = 5
x + 5 = 9
x = 4
So the number is 45. Check:
2(45) - 36 = 54
90 - 36 = 54
54 = 54
2007-10-16 18:21:48 · answer #1 · answered by supensa 6 · 1⤊ 0⤋
1
2007-10-16 17:32:51 · answer #2 · answered by ruffa 2 · 0⤊ 1⤋
45
4 + 5 = 9
45 x 2 = 90, 90 - 36 = 54
I can't help with working it out though, I kinda just guessed the numbers and then checked if they worked out!
2007-10-16 17:26:51 · answer #3 · answered by Anonymous · 0⤊ 0⤋
The number is 45, but I got it by trial and error; I'm not sure how to make an equation.
If this or another answer here proves helpful in your research, you can encourage good answers by choosing one answer as the "best answer."
Cheers,
Bruce
2007-10-16 17:27:23 · answer #4 · answered by Bruce 7 · 0⤊ 0⤋
45
4+5 = 9
45 *2 = 90
90-36 = 54
equations: a+b = 9
I'm sorry my mind has shut down. 45 was a guess. Hopefully you can figure out the general process to get the answer from here. Please let us know.
2007-10-16 17:31:50 · answer #5 · answered by dmontesmom2 4 · 0⤊ 0⤋