Question

Josephine can correct her students test papers in 6 hours, but if her teacher's assistant helps, it would take them 4 hours. How long would it take for the assistant to do it alone? (PLEASE HELP)

Answer 1

Explanation:

Jose rate = 1 job / 6 hrs

assist rate = 1 job / x hrs where x is assistant alone time

now for BOTH of them to finish the one job :

job/ (sum of rates) = time

1 / ( 1/6 + 1/x) = 4 hrs

solve for x = 12 hrs for assistant alone