Arithmetical progression

 A sequence of numbers {Nn} is called an arithmetical progression if Nn+1 = Nn + d or Nn = N0 + n∙d. A sum of n first elements of the sequence Sn = (N0+Nn-1)∙n/2 A growth of a tree is an example of arithmetic progression. A height of a sapling is N0. The tree is gained on d cm per month. Its height through t months Nt = Nt-1 + d or Nt = N0 + t∙d. This model demonstrates a solution for 2 types of problems. In the first a height of sapling, gain per months, and a time period are given and a tree height through the given period is calculated. In the other a height of sapling is calculated depending on the tree height at given period and the gain per month. You can also solve suggested problems and check your answers. Choose the Solve radio button and a type of problem, insert the answer into Answer spinbox and click the check answer button. If you want to see a solution of the problem click the solution button. You cannot change the problem specification in solving mode, but only in demonstration mode. To work with a different problem click the next button.