Q: Five maple trees and six ash trees are on sale for $83. Nine maple trees and eleven ash trees are on sale for $151. What is the cost of an Ash tree.....
I figured this much:
5m + 6a = 83
9m + 11a = 151
I know I have to substitute, but I keep getting a negative number.
2007-09-11 09:31:41 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
5m + 6a = 83
9m + 11a = 151
ok from the 1st one... m = (83-6a)/5
plug it into the second:
9(83-6a)/5 +11a = 151
149.4 - 10.8a + 11a = 151
0.2a = 1.6
a = 8
5m + 48 = 83
m = 7
2007-09-11 09:41:37 · answer #1 · answered by smartretard 2 · 0⤊ 0⤋
for this question, use systems of equations as the method to solve, not substitution.
Multiply the first line by 9 and the second by 5.
(5m + 6a = 83) 9
(9m + 11a = 151) 5
to get two equations where the number of m is equal
i) 45m + 54a = 747
ii)45m + 55a = 755
___________________ (subtract line ii from i)
iii) -a = -8 => a = 8
2007-09-11 09:45:31 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Pick one of the equations and set it up so you have m on one side, and a on the other. For example, m = (83-6a)/5. Then substitute (83-6a)/5 for m in the other equation and solve it for a. This should let you solve for m.
2007-09-11 09:38:33 · answer #3 · answered by John R 7 · 0⤊ 0⤋
Multiply equation #1 by 9:
45m + 54a = 747
Rewrite as 45m = 747 - 54a
Multiply equation #2 by 5:
45m + 55a = 755
Now substitute::
747 - 54a + 55a = 755
747 + a = 755
a = 8
2007-09-11 09:41:24 · answer #4 · answered by Joe 2 · 0⤊ 0⤋