Mary has $2.20 in dimes and nickles. I f she has 10 more dimes than nickles, how many of each coin does she have?
Here is what I have....
.05(D+10)+10D=2.20
.05D+.5+10D=2.20
.15D+.5-.5=2.20-.5
.15D=1.70
where did I go wrong?
2007-03-28 18:56:23 · 6 answers · asked by calired67 4 in Science & Mathematics ➔ Mathematics
I know what the answer is but I can't figure out how to get there from here
2007-03-28 19:01:00 · update #1
d=nickels
d+10=dimes
0.05d + 0.10(d+10) = 2.20
0.05d + 0.10d + 1 = 2.20
0.15d = 1.20
d = 8 nickels
d + 10 = 18 dimes
Check 0.05*8 + 0.10*18 = 0.40 + 1.80 = 2.20
2007-03-28 19:03:57 · answer #1 · answered by ecolink 7 · 1⤊ 0⤋
There are two mistakes in the first line.
Firstly, you need to work in the same units all through. I would suggest cents, rather than dollars as you (mostly) did before.
Secondly, she has more dimes than nickels, so the formulation should be:
5(D - 10)+10D=220
2007-03-28 19:01:51 · answer #2 · answered by Tim N 5 · 1⤊ 0⤋
N+10=D
0.05N + 0.1D =2.20
0.05N + 0.1 (N+10)=2.20
0.15N +1=2.20
N= 1.2/0.15= 8 nickles
So there are 18 dimes
$1.80+ $.40 = $2.20
2007-03-28 19:17:58 · answer #3 · answered by Bomba 7 · 1⤊ 0⤋
The correct answer is 8 nickels and 18 dimes...I just did it by trial and error...i'm not sure exactly how to do it, sorry.
2007-03-28 19:04:18 · answer #4 · answered by stellniel 2 · 0⤊ 0⤋
she has 8 nickels=.40 and 18 dimes=1.80
2007-03-28 18:59:39 · answer #5 · answered by ms.m 2 · 1⤊ 0⤋
.1D+.05N=2.20
D=N+10
.1(N+10)+.05N=2.2
.1N+1+.05N=2.2
.15N=1.2
N=8
D=18
2007-03-28 19:05:16 · answer #6 · answered by tpk_april1 5 · 1⤊ 0⤋