There're three distinct whole numbers a,b,c displayed on three cards. In each round, each of three students picks one card randomly in turn then record their numbers. They play at least two rounds. If after the last round, the 1^st one gets 20 points totally, the 2^nd one gets 10, the 3^rd one gets 9 and the 2^nd one picks number c at the last round, then who picks number b at the first round?

A. The 1^st one

B. The 2^nd one

C. The 3^rd one

D. Can't be found out

The last digit of the value of A = 2¹ + 3⁵ + 4⁹ + 5¹³+ ... + 2004⁸⁰⁰⁹ is

thank oyu

hiểu đc mấy chữ cuối

There're four black box and each box has the same number of marbles. Only one of the following statements is correct about the number of marbles in it.

- Five or Six

- Seven or Eight

- Six or Seven

- Seven or Five

How many marbles are there in each box?

Two people need to finish a work. The first person can finish the work by himself in \(\frac{2}{5}\)hours. At first, the first person does it alone and then 12 minutes later the second person join to work together. Two people work in \(\frac{1}{9}\) hours, then complete the work. How long does it take the second person to finish the work all by himself?