An orange costs $.09. How much would 2 dozen oranges cost?

Another way of thinking about it that may help you do things like this in your head. If you wished to do so.

##$2.16##

##color(brown)("There is no reason why you should not write down a few numbers")## ##color(brown)("but still do a lot of the working out in your head.")##

Doing it is much quicker than explaining it '~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The calculation we need to do is ##24xx$0.09## Let's explore another way of doing it.....

1 dozen is 12, so 2 dozen is ##2xx12##

But ##12 = 10+2##

Multiplying a number by 10 or 2 is much easier than multiplying by 12. '~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ##10xx$0.09 = $0.90## ##color(white)(1)2xx$0.09=ul($0.18)" "larr" add"## ##" "$1.08## '~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ So ##12xx$0.09=$1.08##

So ##24xx$0.09=2xx$1.08= $2.16##