Buy a bottle of shampoo 30 yuan to buy 5 Ping free 1 bottle to buy 8 bottles to buy 2 bottles, my mother and colleagues to buy 12 bottles, how to buy cost-effective?

Buy a bottle of shampoo 30 yuan to buy 5 Ping free 1 bottle to buy 8 bottles to buy 2 bottles, my mother and colleagues to buy 12 bottles, how to buy cost-effective?

If you buy five bottles twice and give two bottles away, that's 25 yuan a bottle

In order to promote sales, a store will sell a shampoo with a price of 30 yuan per shampoo at the price of 40 yuan per shampoo. After two price cuts, it will be adjusted to 32.4 yuan per shampoo. If the price reduction rates of the two price cuts are the same, calculate the price reduction rate

Set the price reduction rate to X
Price after the first price reduction: 40 * (1-x)
Price after the second price reduction: 40 * (1-x) * (1-x) = 32.4
(1-X)*(1-X)=32.4/40=81/100=9^2/10^2
1-X=9/10
X=1/10=10%

Uncle Zhang went to buy oil and saw that the same kind of oil has different promotion strategies in two supermarkets: supermarket a costs 12 yuan per bottle, four for one free; supermarket B costs 12 yuan per bottle, 15% off
Which supermarket is more cost-effective?

12* 4=48
48 / 5 = 9.6 yuan / bottle
12 * 0.85 = 10.2 yuan / bottle
It's more cost-effective to go to a supermarket

Uncle Li went to buy fresh orange juice, and saw that the same kind of fresh orange juice had different promotion strategies in two supermarkets. Supermarket a: 12 yuan per bottle, buy four get one free; supermarket B: 12 yuan per bottle, 15% discount
Uncle Zhang wants to buy 5 bottles of fresh orange juice. Which supermarket is suitable for him?

A: CO production: 12 * 4 = 48 yuan
B: total flowers: 12 * 5 * 0.85 = 60 * 0.85 = 51 yuan
therefore
It's a good deal to go to a supermarket