a man has $.70 in dimes and nickels. he has 8 coins altogether. how many nickels does he have

Question

I'm confused and i need so help asap

Answer 1

let d= dimes and n= nickels

 

a dime is .10 cents and nickel .05 cents

 

 

.10d + .05n = .70 , 100 ( .10d + .05n = .70) = 10d +5n = 70 , mulitiply by 100 easier to work with

 

    d + n = 8 , so n= 8-d if you subtract d from both sides

 

so substitute n= 8-d into the equation 10 d + 5n= 70

                                                       10 d + 5(8-d) = 70

                                                       10 d + 40 -5d =70                   

                                                        5d+40= 70

                                                         5d = 70 - 40 (subtract 40 from  both sides)

                                                          5d= 30

                                                             d=6

 

d+n= 8

6 +n =8

 

So there are 6 dimes, so how many nickels???