gnarbot,
Think of the ratio as two parts to a larger "whole".
Since we know that the ratio is 3 nickels to 4 dimes add the two "parts together". 3 + 4 = 7
Now, since we know that there are 28 coins total, divide the "whole" ratio. You get 28/7 = 4
Now multiply the dime "part" of the ratio by the multiplier you just solved for to get the number of dimes. 4 x 4 = 16
There should be $1.60 worth of dimes.
To check the math, multiply the nickels "part" by the multiplier as well (4 x 3 = 12). 12:16 is the same as 3:4 so that should be the answer.
Thanks that seems to make sense but why wouldn't my way work?