Three fifths of the tshirts in a tshirt shop are blue. Five eighths are those tshirts are on sale. One third of the blue tshirts that are on sale are size medium. What fraction of the shops tshirts are blue tshirts that are on sale and are size medium. Explain.
number of t-shirts ---- x
blue t-shirts = (3/5)x = 3x/5
blue shirts on sale = (5/8)(3x/5) = 15x/40 = 3x/8
blue shirts on sale which are medium = (1/3)(3x/8) = x/8
fraction the above is of the total = (x/8) / x = 1/8
check: suppose you had 120 t-shirts
blue ---- (3/5)(120) = 72
on sale = (5/8)(72) = 45
medium size = (1/3)(45) = 15
15/120 = 1/8