Joshua paid his friend a simple annual interest of 10%.
Step-by-step explanation:
As Joshua borrowed $1,000 from his friend and paid him back $1,050 in six months, we can affirm that he paid $50 of interest after six months. So, as after half a year he paid a $50 interest, he would have paid $100 after a year. As 100 is the 10% of 1000, we can say that he paid his friend a simple annual interest of 10%.
