SOLUTION: Your piggy bank contains $19.75 in dimes and quarters. There are 100 coins in all. How many dimes are there?

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Question 570850: Your piggy bank contains $19.75 in dimes and quarters. There are 100 coins in all. How many dimes are there?
Answer by JBarnum(2146) About Me  (Show Source):
You can put this solution on YOUR website!
these are fun questions, brings me back to learning to count with money..anyway
dimes(d) and quarters(q)
given
dimes are worth .10 and quarters are worth .25
.10%28d%29%2B.25%28q%29=19.75
d%2Bq=100
.
to solve for (d) you must substitute for (q)
q=highlight%28100-d%29
.10%28d%29%2B.25%28q%29=19.75
.10%28d%29%2B.25%28highlight%28100-d%29%29=19.75
.10d%2B25-.25d=19.75
25-.15d=19.75
25=19.75%2B.15d
25-19.75=.15d
5.25=.15d
highlight%2835=d%29