A Pennsylvania high school has apologised after students were given a maths homework assignment that asked which family member had sexually assaulted a girl.
The assignment focused on Maya Angelou and her autobiography I Know Why The Caged Bird Sings.
It provided an algebra formula that asked: "Angelou was sexually abused by her mother's ___ at age 8, which shaped her career choices and motivation for writing."
Pennridge High School students needed to solve the formula before deciding whether the answer was boyfriend, brother or father.
Screenshots of the homework posted by news organisations showed the subsequent question reads: "Trying to support her son as a single mother, she worked as a pimp, prostitute and ___."
Another formula must be solved to determine if the answer was bookie, drug dealer or nightclub dancer.
The homework was coupled with a word puzzle about the book and author, The Intelligencer newspaper reported.
The assignment was from a website that allows teachers around the world to share resources.
"We apologise to anyone who was offended by the content of the assignment and have taken steps to avoid such occurrences in the future," Pennridge Superintendent Jacqueline Rattigan said in a statement, adding that the district had received complaints.
A similar homework assignment caused controversy in Fort Myers, Florida, in 2015.
In that case, a middle school teacher also downloaded the algebra homework from an external website.
The district said the veteran teacher did not carefully examine the homework and called it an oversight that would not be repeated.
I Know Why The Caged Bird Sings, published in 1969, is assigned reading in many US high schools, but is also occasionally attacked for its content.
Angelou's passages about her rape and teenage pregnancy have made it a perennial on the American Library Association's list of works that draw complaints from parents and educators.
"'I thought that it was a mild book. There's no profanity," Angelou, who died in 2014, told the Associated Press.
"It speaks about surviving, and it really doesn't make ogres of many people.
"I was shocked to find there were people who really wanted it banned, and I still believe people who are against the book have never read the book."