Erin's Donuts are the best. They cost $0.40 per donut, or you can buy a dozen and get $1.50 off. Only 5 blocks away, they have Anne's Donuts, and they are just as good. The donuts cost $0.50 each at Anne's Donuts, or you can buy a dozen and $2.10 off. You need to buy 16 donuts for a party. Which store would cost the least?
Erin's Donuts: $0.40 per donut, $1.50 off for a dozen
1 dozen = 12 units
so, a dozen cost = 0.4 * 12 - 15 = 4.8 - 1.5 = $3.3
16 - 12 = 4 donuts
so, Erin cost = 0.4 * 4 + 3.3 = 1.6 + 3.3 = $4.9
Anne's Donuts: $0.5 per donut, $2.10 off for a dozen
so, a dozen cost = 0.5 * 12 - 2.10 = 6 - 2.10 = $3.9
16 - 12 = 4 donuts
so, Anne cost = 0.5 * 4 + 3.9 = 2 + 3.9 = $5.9
because 4.9 < 5.9
so, Erin Donuts cost the least.
