Length of a piece of string is 27 cm rounded to the nearest centimetres what is the lower bound of the length of the piece of string

What are the values of each variable in the diagram below?

In a singing competition, there are 150 participants. at the end of each round, 40% of the participants are eliminated. how many participants are left after n rounds?

Travis and paula went to lunch.travis ordered a sandwich for $7.50 and paula ordered a burger for $5.25.after lunch,they left a 15% tip for the waiter.how many money did they spend altogether?