I am too dumb to help my 8th grader with her math. Any smart people out there can you solve this word problem

Question

Johnny has 40 coins in all. He has nickels, dimes and quarters and they all equal $4.05. He has 7 more nickels than dimes. How many quarters does he have??? Must show work.

Answer 1

40 coins: n+d+q=40

7 more nickels than dimes: n=d+7

=> d+7+d+q=40 =>2d+q=33 =>q=33-2d

plug n=d+7 , d=d, q=33-2d

into

.05n+.1d+.25q=4.05

results in

.05(7+d)+.1d+.25(33-2d)=4.05

results in d=13
n=20
q=7


POINTS ME!

Answer 2

I don't agree about the amount of rudeness that was thrown your way by some, but I do have a suggestion. Get off Yahoo Answers, and go to the library and open up a book on math. You may become enlightened, and then won't label yourself as "dumb" in math. I teach math, and I get mad at students who say that about themselves. Asking questions about the hair on testicles isn't a productive use of your time if you are trying to raise kids. (lol...just kidding...it is perfectly your right to be curiuos about such things!) But yuck!

First of all, you could use trial and error...but here is the math way:

OK, here you go:

nickels + dimes + quarters = 40 (since there are 40 coins)

Abbreviate with:

N + D + Q = 40

Now, as a review, if you have two quarters, you could write the following:

2 (0.25) = 0.50

If you add three dimes to that, then:

2 (0.25) + 3 (0.10) = 0.80

If one says you have seven more nickels than dimes, then you could say:

N = 7 + D

That is the same thing as saying if you have some dimes, then the number of nickels you have equals the number of dimes plus seven.

Do you get that?

Ok, let's continue:

N + D + Q = 40
(7 + D) + D + Q = 40 ..... {equation 1}

Also, each coin is worth so much money. So:

(0.05) N + (0.10) D + (0.25) Q = 4.05

or...since there are 7 more nickels than dimes...

(0.05) (D + 7) + (0.10) D + (0.25) Q = 4.05...... {equation 2}

In math speak, we have two equations and two unknowns. Go to equation 1, and get the Q by itself:

(7 + D) + D + Q = 40

Q = 40 - D - D - 7, you could write this as:

Q = 40 - 2D - 7, or combining the numbers:

Q = 33 - 2D

Now, substitute Q into equation 2 to solve for D:

(0.05) (D + 7) + (0.10) D + (0.25) (33-2D) = 4.05

You will need your algebra skills here, use distribution:

0.05D + 0.35 + 0.10D + 8.25 - 0.50D = 4.05

Combine D's and numbers:

-0.35D + 8.60 = 4.05

Add 0.35D to both sides, subtract 4.05 from both sides:

4.55 = 0.35D

Finally, divide by 0.35

D = 13 dimes (that is part of the answer)

N = 20 nickels (there are seven more than dimes)

Q = 7 quarters (for a total 40 coins)

This is not an 8th grade problem...more like 10th or 11th. If your kid shows up with that work, you better be honest with the teacher and tell them it was so hard you had to get outside help. Don't pass it off as 8th grade work, I as a teacher, wouldn't believe it!

Answer 3

as an australian i don't know what nickel, quarter or dimes are, but i know the principle
1st we are given the limitation
aX+bY+cZ = 4.05 (1)
where a = value of nickel
b = value of dime
c= value of quarter
X = number of nickels
Y = number of dimes
Z = number of quarters
sub values a,b &c in (I would do this if i knew)
so equation (1) means the value of a nickel, times the amount of nickels, plus the value of a dime, times the amount of dimes, plus the value of a quarter plus the value of a quarter equals your total $ value which was 4.05
we also know that
X = 7 +Y (2) <-their are 7 more nickels than dimes
and we know that X+Y+Z = 40 (3) <-- their are 40 coins all up
subing (2) into (1) and (3) you get two simultaneous equations
you can then sub (1) into (3) to find out one value (Y or Z)
sub this into your modified (1) or (3) to get another value (either Y or Z based on what you did before) and sub your Y value into (2) to get your X value
given that the guy above clarified a qaurter is .25, a dime is .1 and a nickel is .05
.05X +.1Y+.25Z = 4.05 (1)
X = 7+Y (2)
X + Y + Z = 40 (3)
sub (2) into (1) and (3)
.05(7+Y) +.1Y +.25Z=4.05
.15Y +.25Z=3.7 (4)
(7+Y) +Y + Z = 40
2Y + Z = 33
Z=33-2Y (5)
sub (5) into (4)
.15Y + .25 (33-2Y) = 3.7
.35Y = 4.55
Y=13 (6)
sub(6) into (5)
Z = 33-2 x 13
Z = 7
sub Y into (2)
X = 7+13
X = 20
therefore you have
20 nickels,
13 dimes, and
7 quarters

Answer 4

Ok Ok, start with setting up an equation and values for each theoretical coin's value denomination. In this case, we'll go x for nickels, y for dimes a z for quarters. Since we are solving for quarters, we'll put Z on the numerator above the yx denominators. The right side of the equation is the number 4.05, for which we will susequently chart out a reverse absolute value, using a standard deviation of 2 and a graphing calculator. Because there are a total of 40 coins and 40 is an even number, we want to be sure that it is treated evenly. As such, we will ahhhh crap i dont know sorry. i tried

Answer 5

7 Quarters = $1.75
20 Nickels = $1.00
13 Dimes = $1.30

7 + 20 + 13 = 40 Coins

$1.75 + $1.00 + $1.30 = $4.05

Answer 6

1) n + d + q = 40
2) 5n + 10 d + 25q = 405 cents ($4.05)
3) n = d + 7; we substitute n in 1) and 2)

1) d + 7 + d + q = 40; --> 2d + q = 33
2) 5(d+7) + 10d + 25q = 405 --> 5d + 35 + 10d + 25q = 405
15d +25q = 370

1) 2d + q = 33 --> q = 33 - 2d (4)
2) 15d +25q = 370; substitute again (4) in (2)

15d + 25(33 - 2d) = 370
15d + 825 -50d = 370
-35d = 370 - 825 (multiply by (-1) --> 35d = 455

d = 455/35 = 13 dimes
n = d + 7 = 13 + 7 = 20 nickels; from eq (3)
q = 33 - 2d = 33 - 2(13) = 7 quarters; from eq (4)

Answer 7

OK that took me forever!!!!
here goes

20 nickels =$1.00
13 dimes =$ 1.30
7 quarters = $ 1.75

20 nickels +13 dimes + 7 quarters =40 coins
$1.00+ $1.30+ $ 1.75=$4.05
I hope I have helped GOOD LUCK IN SCHOOL IN THE FUTURE

Answer 8

WHY WHY WHY Do they do this to US parents?!?!?!? LOL

I can't even do 6th grade math - Geometry OR 9th grade Algebra! LOL I hope to heck I can MASTER 1st grade this year! LOL

Ya got me hanging. I wish I knew the answer for you!

A quarter = 0.25 Cents
A dime = 0.10 Cents
A nickel = 0.05 cents

DO NOT FORGET THERE HAS TO BE 40 COINS TOTAL THAT = $4.05!

WOW thanks for the fast work on this problem!!!

Answer 9

I don't know how either! I taught 5th grade science and social st. and sometimes would have to tutor math much to my dismay! The kids used so many different things than the way I was taught. I could not figure one thing out and asked the math teacher and she said she had made it up as a teaching method! No wonder I didn't know what they were talking about! The kids would say math is not your thinghuh, ms---? I had to agree!I struggled through hs math with my oldest son but thank goodness the other two didn't need help!

Answer 10

johnny has 40 coins dimes, nickels, quarters,
and has seven more nickels than dimes how many quarters does johnny have (bellow)

Nickels 35 cents|
|
Dimes 70______ $4.05
|
Quarters 3.00 |

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