Saturday

April 19, 2014

April 19, 2014

Posted by **kathryn** on Saturday, April 20, 2013 at 5:54pm.

2. A vending machine that takes only dimes and quarters contains 30 coins, with a total value of $4.20. How many of each coin are there?

- math -
**DW**, Saturday, April 20, 2013 at 6:36pmthis is similar to the question I answered on the question after this:

pretend nickels=x

dimes=y

x+y=21 *total number of dimes and nickels is 21

.05x+.1y=$1.65 *the value of x is .5 and the value of y is .1 so when you multiply it by the number of x and y you get $1.65

now use elimination:

first solve for one variable

x+y=21

y=-x+21

now plug "x+21" as "y" in the other equation

.05x+.1(-x+21)=$1.65

.05x-.1x+2.1=1.65 *distribute

-.05x=-.45

x=9

now plug 9 as x into the first equation

x+y=21

9+y=21

y=12

she has 9 nickels and 12 dimes

check by plugging in answers into both equations:

9+12=21 *correct

and

.05(9)+.1(12)=1.65 *correct

now apply the same concept to number 2

- math -
**Anonymous**, Wednesday, March 12, 2014 at 8:56am22 Dimes

8 quarters

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