Kate has 21 coins (nickels and dimes) in her purse. How many nickels and dimes does she have if she has $1.50?

Question

do this in substitution

Answer 1

Let n = #nickels, d = #dimes

 

n + d = 21   total coins equation

 

So d = 21 - n

 

5n + 10d = 150 (n worth 5c, d worth 10c, total = 150c)

substituting:  5n + 10(21 -n) = 150

                    5n + 210 - 10n = 150

                                    - 5n = -60

                                        n = 12, so d = 21 -12 =9

12 nickels, 9 dimes ANSWER

Answer 2

Hi Michael,

So if we know that #nickels + #dimes = 21coins

And nickels + dimes = $1.50

We can say:

0.05x+0.10(21-x)=1.50

If you solve for x, you'll know how many nickels she has. 21-x is the number of dimes she has.