What is #9.5 mm +17.286 mm - 1.4445 mm# ?

1 Answer

#25.3415mm#

Explanation:

Since the units are all the same, I'll drop them for the purposes of adding/subtracting the numbers together.

We work from left to right, which means we do this first:

#color(white)(0)9.5#
#ul(17.286)#
#26.786#

Now we can do the subtraction:

#26.786#
#ul(color(white)(0)1.4445)#

See that the #26.786# doesn't have enough digits, and so we put in 0 as a place holder:

#26.7860#
#ul(color(white)(0)1.4445)#

We start from the right and move left. First we have #0-5# which doesn't work, and so we borrow from the 6 next to the 0. The 6 is reduces by 1 to 5 (we've borrowed 1) but because we're getting it from the next place up, it's worth 10 to the next place down:

#26.78cancel(6)^5cancel(0)^10#
#ul(color(white)(0)1.444color(white)(0)5)#

#10-5=5#:

#26.78cancel(6)^5cancel(0)^10#
#ul(color(white)(0)1.444color(white)(0)5)#
#color(white)(0000000)5#

And we can do the rest of the subtractions:

#26.78cancel(6)^5cancel(0)^10#
#ul(color(white)(0)1.444color(white)(0)5)#
#25.341color(white)(0)5#

Giving #25.3415mm#