The cost of 9 trousers is $72 . Find the cost of 12 trousers

x=96

Step-by-step explanation:

We can solve by writing ratios

9 trousers             12 trousers

=

72 dollars              x dollars

Using cross products

9x = 12 *72

9x =864

Divide by 9

9x/9 = 864/9

x=96

we have three similar triangles, because each has a right angle and shares an angle.   let's write the angles in order: opposite to short leg, long leg, hypotenuse.

cab similar to bad similar to cbd

or as ratios,

ca: ab: cb = ba: ad: bd = cb: bd: cd

we also know

ac = ad + cd

(ad+cd): ab: cb = ba: ad: bd = cb: bd: cd

(ad+cd)/cb=cb/cd

we have cb=6, ad=5 and seek x=cd.

we reject the negative root and conclude x=4

answer: 4