Donna bought a candy bar for 1.50.She paid with nickels and dimes. She used 21 coins in all. How many nickels (n) and how many dimes (d) did she use?
Okay, so this is a problem involving systems of equations. We would set up this system as follows:
n+d=21 (number of coins)
5n+10d=150 (amount of money)
For the second equation, I find it easier to remove the decimal places altogether and write it in cents instead. We can then rearrange the first equation as n=21-d and substitute that into the second. The second equation then becomes 5(21-d)+10d=150. Writing the terms out and simplifying gives us 5d=45, which becomes d=9. Therefore, we have 9 dimes. Plugging that value into the first equation gives us n=12. This means we have 12 nickels. We then double-check, and it all works out. Hopefully, this helps! - BasicMaths
(note: in the system of equations above, n stands for nickels and d for dimes)
"Mathematics is not about numbers, equations, computations, or algorithms: it is about understanding." - William Paul Thurston