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robert has 50 coins, all in nickels and dimes, amounting to $3.50. how many nickels does he have?
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Similar problems were solved so many times, that I'd like to offer you a non-traditional solution.
Let us suppose for a moment that all 50 coins are dimes.
Then their value is 50*10 = 500 cents = $5. It is more than $3.50 exactly in $1.50 = 150 cents.
It is clear that the difference is due to presence of 5-cent nickels that we intently counted as 10-cent dimes.
It is also clear that the number of these 5-cent coins is = = 30 to compensate the difference.
So, the answer is: there are 30 of 5-cent nickels and 50-30 = 20 of 10-cent dimes.
Answer. There are 30 nickels and 20 dimes.
For more traditional solutions see the lessons
- Coin problems
- More Coin problems
- Kevin and Randy Muise have a jar containing coins
- Typical coin problems from the archive
in this site.