Math questions

Question

1)One day a girl bought 20 first class stamps and 10 postcard stamps for 15.10 dollars another day she spent 33.10 on 40 first day stamps and and 30 on postcard stamps . Find the cost of each stamps.

 

 

2)Lisa invested 32,000 in two accounts one yielding 6 percent and another yielding 9 percent if she received a total of 2,490 in interest at the end of the year . How much did she invest in each account.

Answer 1

Let F = cost of one 1st class stamp & P = cost of one postcard stamp.

 

One day: 20F + 10P = 15.10

Another day: 40F + 30P = 33.10

 

Two equations, two unknowns--solve the system!

 

2) Let X = $ amount put into account @ 6%, so the rest (32,000-X is invested at 9%.

 

Then total interest earned = 2490 = X(.06) + (32,000-X)(.09); one equation...solve for x.