At the end of the day Mrs Smith counted the days receipts Sh

At the end of the day, Mrs. Smith counted the day\'s receipts. She deposited the $5 and $10 bills in the vault. She deposited 31 bills for a total of $225. How many $10 bills did she deposit in the vault? Solve using intercepts.

Solution

let Mrs. Smith deposited x $10 bills and y $5 bills

She deposited 31 bills for a total of $225

hence x+y=31 and 10x+5y=225

we want to find how mane $10 bills she deposited.

that is we need to find x.

we have x+y=31 hence y=31-x

so 10x+5y=225

or, 10x+5(31-x)=225

or, 10x-5x+155=225

or, 5x=225-155=70

hence x=70/5=14

she deposited 14 $10 bills in the vault [answer]