先涨价再打八折，和直接打八折，哪个更便宜？
Is raising the price first then giving 20% off cheaper than a straight 20% off?
直接打八折更便宜。先涨后降实际是（原价×1.1）×0.8=0.88倍原价，而直接八折是0.8倍原价，前者多付约8%。
The straight 20% off is cheaper. Mark-up-then-discount gives (price×1.1)×0.8=0.88 of the original, while a direct 20% off gives 0.8, so the trick costs about 8% more.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
Beckmann, S., 《中小学数学教师数学》(第4版), Pearson
Beckmann, S., 'Mathematics for Elementary Teachers' (4th ed.), Pearson
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL18708410W：Mathematics for elemen
#生活中的数学 #折扣陷阱
抢红包时金额是怎么随机分配的？
How are amounts randomly assigned in a red-packet grab?
常用二倍均值法：每次在0到剩余人均两倍之间随机，保证先抢不会必多、后抢也有机会。它利用了均匀分布与期望值控制。
A common method is the double-mean rule: each draw is uniform between 0 and twice the remaining average, so early grabbers are not guaranteed more. It uses uniform distribution with controlled expectation.
难度 进阶 · 适合 大众
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：本题原挂出处与答案内容不符，已撤回；具体书目待补，暂不展示来源。
本题原挂出处与答案内容不符，已撤回；具体书目待补。
Previous citation withdrawn as unsupported for this answer; a specific source is pending.
#生活中的数学 #随机
双十一满300减50，实际是打几折？
What discount is a spend-300-get-50-off promotion?
正好凑到300元时，实付250元，相当于约八三折。但如果为了凑单多买了不需要的东西，实际并不省钱。
At exactly 300 yuan you pay 250, about an 83% (8.3-fold) discount. But buying extras just to qualify often means you do not actually save.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
Beckmann, S., 《中小学数学教师数学》(第4版), Pearson
Beckmann, S., 'Mathematics for Elementary Teachers' (4th ed.), Pearson
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL18708410W：Mathematics for elemen
#生活中的数学 #满减
买二送一和打七折哪个划算?学会比较就不吃亏
Buy two get one free versus thirty percent off — which deal wins?
算单价就一目了然:买二送一等于花两份钱拿三份,每份约原价67%;打七折是每份70%。所以买二送一略胜——但前提是你本来就需要三份!为了优惠买不需要的东西,省下的其实是负数。比较思维比优惠本身更有价值。
Compare unit prices: buy-two-get-one means paying twice for three items — about sixty-seven percent each; thirty percent off is seventy. Buy-two wins slightly — if you truly need three! Buying unneeded stuff for discounts saves a negative. Comparison thinking beats coupons themselves.
难度 进阶 · 适合 小学低段(6-8)
CC BY 4.0 · 已核验 · Verified 2026-11-02
来源 · Source
《数学花园漫游记》,马希文,中国少年儿童出版社,2004
Ma Xiwen, Adventures in the Math Garden, China Children Press, 2004
独立核验依据 · Independent verification: 核验依据 1 ISBN 9787500767558（豆瓣书目条目: 数学花园漫游记）
#折扣比较 #单价 #消费数学
买一送一和第二件半价，哪个更划算？
Which is better, buy-one-get-one-free or the second item half price?
买一送一相当于花一份钱得两件，即五折；第二件半价是两件共花一点五份钱，相当于七五折。所以买一送一更划算。
Buy-one-get-one-free means paying one price for two items, a 50% discount; the second at half price costs 1.5 prices for two, a 25% discount. So BOGO is better.
难度 入门 · 适合 小学低段(6-8)
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
Beckmann, S., 《中小学数学教师数学》(第4版), Pearson
Beckmann, S., 'Mathematics for Elementary Teachers' (4th ed.), Pearson
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL18708410W：Mathematics for elemen
#生活中的数学 #折扣
量身高的时候为什么要贴着墙站直?尺子上的数字是什么意思?
Why stand tall against the wall when measuring height? What do ruler numbers mean?
贴墙站直,从头到脚才是一条直线,量得才准。尺子上的数字是「长度密码」:相邻两个数字间隔一样长,是一厘米或一寸。数字越大越长——明年再量,你又长高几格!
Standing straight against the wall measures one true line head to toe. Ruler numbers are length codes: gaps between neighbors are all equal — one centimeter or inch. Bigger numbers mean longer. Measure again next year and you will climb a few more marks.
难度 入门 · 适合 幼儿(3-6)
CC BY 4.0 · 已核验 · Verified 2026-11-02
来源 · Source
《数学花园漫游记》,马希文,中国少年儿童出版社,2004
Ma Xiwen, Adventures in the Math Garden, China Children Press, 2004
独立核验依据 · Independent verification: 核验依据 1 ISBN 9787500767558（豆瓣书目条目: 数学花园漫游记）
#测量 #尺子 #长高