## ihatealgebrasomuch can someone please explain to me how to use ratios? i completely forgot and need to know them for a test tomorrow! heres the question- The ratio of 2 consecutive sides of a parallelogram is 7:9. If the perimeter is 224cm, what is the length of the sides? one year ago one year ago

1. phi

this is more than just ratios. You have to know that opposite sides of a parallelogram are equal. You have 4 sides, |dw:1355358477849:dw| you also have to know that the perimeter is the distance around the figure, or the sum of lengths of all the sides: a+b+a+b= 2a+2b 2a+2b= perimeter you now can set this to 224 cm and simplify: 2a+2b= 224 cm a+b= 112 (divide both sides, all terms by 2) now you can use the ratio idea a:b= 7:9 (side a is to side b as 7 is to 9) or (I like it this way) $\frac{a}{b}= \frac{7}{9}$ at this point we "solve" for either a or b. Let's solve for "a". multiply both sides by b: $\frac{a}{\cancel{b}}\cdot \cancel{b}= \frac{7b}{9}$ this says $a= \frac{7b}{9}$ replace a in your "perimeter equation" a+b= 112 $\frac{7b}{9} + b= 112$ if we put b over the "common denominator" of 9, we get $\frac{7b}{9}+ \frac{9b}{9}= 112$ add fractions $\frac{16b}{9}= 112$ multiply both sides by 9/16, to solve for b $b= \frac{9}{16}\cdot 112$ after doing the arithmetic you get b=63 can you find a ?

2. Tabbiejack

I am trying to graph it and I am the worst

3. ihatealgebrasomuch

so basically, it would look like this? |dw:1355359130294:dw| and then set them equal to 224 and get x=7 so the side lengths are 63 and 49?

4. phi

yes that is a nice way to do it

5. Tabbiejack

The options are much different