Question

Your piggy bank has a total of 40 coins in it; some are dimes and some are nickels. If you have a total of $3.50, how many dimes do you have?
Answer







30








10








40








20


Your piggy bank has a total of 40 coins in it; some are dimes and some are nickels. If you have a total of $3.50, how many dimes do you have?
Answer







30








10








40








20

@Mathematics

Answer 1

x + y = 40
.05x + .10y = 3.50

y = 40 - x
y = (3.50 - .05x)/.10

y = y

.10(40 - x) = 3.50 - .05x

4 - .1x = 3.50 - .05x
4 - 3.50 = .05x
.50 = .05x
x = .50/.05 = 10
y = 30

so she has 30 dimes