Question 988424

 A jar contains 40 coins consisting of dimes and quarters and having a total value of $4.90.   How many of each kind of coin are there?


Having problems figuring out the word problem. 

I have.  d + q = 40

And

.1d + .25q = 4.90

Can you show me how to do it?
<pre>There's no NEED to multiply the 2nd equation by 100 as 1 person suggested. Don't let anyone tell you RUBBISH!
d + q = 40____d = 40 - q ------ eq(i)
.1d + .25q = 4.9 ------ eq (ii)
The EASIEST "route" is the one that involves substituting 40 - q for d in eq (ii). 
This gives: .1(40 - q) + .25q = 4.9
4 - .1q + .25q = 4.9
.15q = .9
Number of quarters, or {{{highlight_green(matrix(1,5, q, "=", .9/.15, "=", 6))}}}
Now, substitute 6 for q in eq (i) to get "d," the number of dimes.
There's ABSOLUTELY nothing wrong with working with decimals!