Joe has a collection of nickels and dimes that is worth $3.95. If the number of dimes was doubled and the number of nickels was increased by 21, the value of the coins would be $8.40. How many nickels and dimes does he have?

Question

anonymous · Answer

Let n be the number of nickles and d be the number of dimes.  Then one equation is$$.05n+.10d=3.95$$and a second equation is$$.05(n+21)+.10*2d=8.40$$Solving this system will give the answer

anonymous · Answer

can someone please help Thanks!

anonymous · Answer

He has enough to buy a happy meal.

curry · Answer

with wat do iu need help

anonymous · Answer

help with solving

curry · Answer

post

anonymous · Answer

Multiply the first equation by 2 to get$$.1n+.2d=7.9$$and then solve it for .2d$$.2d=7.9-.1n$$(continued)

anonymous · Answer

Distribute the .05 in the second equation$$.05n+1.05+.2d=8.4$$now substitute 7.9-.1n (from the last line in my previous post) in for the .2d in the equation above$$.05n+1.05+7.9-.1n=8.4$$This gives you an equation with a single variable, n. Solve for n. 
(continued)

anonymous · Answer

N = Nickels, D = Dimes
So....N + D = 3.95
If he has 21 Nickels that means he has $1.05
So N = 1.05
1.05 + D = 8.40
D = 8.40 - 1.05
D = $7.35
Divide 7.35 by 10, hes got about 73 dimes

anonymous · Answer

right?

anonymous · Answer

Thanks gylvx Yes

anonymous · Answer

mandolino hes a kid, don't give him university equations lol

anonymous · Answer

it scares the pellet out of people that aren't math majors :D

anonymous · Answer

wait i didnt read the question properly

anonymous · Answer

ohk

anonymous · Answer

$$.05n-.1n=8.4-7.9-1.05$$$$-.05n=-.55$$$$n=\frac{.55}{.05}=11$$This is the number of nickles.  To get the number of dimes substittute this value for n in any of the above equations$$.2d=7.9-.1n$$or$$.2d=7.9-.1(11)$$$$d=\frac{7.9-.1(11)}{.2}=34$$This the number of dimes.

anonymous · Answer

joy
what grade are you in?

anonymous · Answer

Thank you Mandolino...:)

anonymous · Answer

I wish I would have kept my other medals..

anonymous · Answer

how do you give medals?

anonymous · Answer

@joy, You know, another way that might not seem so complicated would be to multiply each equation through by 100 to convert all the decimals to whole numbers.  The process from there could be the same, but the arithmetic might seem easier.

You are welcome for the help.

anonymous · Answer

Thank you so much again...great explanation..I got it now