if she knit 15 cm in 3 nights, and we want to find how many cm she would knit in 4 nights, we create the following proportion, calling "x"" the number of cm we need to find
15/3 = x/4
meaning: 15 cm is to 3 nights the same as x cm is to 4 nights
and solve for the unknown "x"
multiply by 4 both sides in order to isolate "x"on the right:
15 * 4 / 3 = x
operate
20 = x
therefore, she sould knit 20 cm in 4 nights.
