10.22 放狗

xx_123

只记得简单的几道题。。。大家主要复习方法

PS There is square 20x20, its area is added by 84, each side is added by equal amount, what are the new side value

PS a + b + c together spend 20min to finsh a work a spend 240min to finish alone b spend 40 min to finish alone how long does it take c to finish alone

PS in z country there are three type of coins in different value make two  equations cross out one variable and u hav the answer

DS there is bag with red blue yellow marble, posibility of taking red marble out of the bag? 1. total number of marble 2. red marble ratio to other two marble

DS pick 5 ppl out of 3 divison  divisions 5 ppl in a 4ppl in b 3 ppl in c, picking 2 from a, 2 from b, 1 from c, how many posibility are there (复习combination)