Below is an instruction that describes a task. Write a response that appropriately completes the request in Swahili. Please answer in Swahili.

### Instruction:
Cameron is printing her thesis in the school library and has 400 A4 pieces of paper. If 40% of the papers did not print out up to her desired quality and she separated them as invalid, calculate the total number of valid documents.

### Response:
 Ikiwa alikuwa na karatasi 400, idadi jumla ya nyaraka alizotenga kama zisizofaa ni 40/100 * 400 kurasa = <<40/100*400=160>>160 kurasa.
Idadi ya nyaraka halali ni 400 kurasa - 160 kurasa = <<400-160=240>>240 kurasa.