How old was Joseph Smith Jr. when he died?
Short answer: 38 years old
“Joseph Smith, Jr. was killed by an angry mob at the jail in Carthage, Illinois on June 27, 1844. He was 38 years old.” - Answers.com
“On June 27, 1844, 38 year-old Joseph Smith and his brother were assassinated by enemies of the Church.” - Chacha.com
“A crew from an English TV station filmed this year’s commemoration. There were recollections of that afternoon in 1844 when the Prophet Joseph Smith, 38, and his brother Hyrum, 44, were martyred in the jail. The martyrdom was witnessed by Elders John Taylor, 35, and Willard Richards, 40, who also were in the jail. The foursome was vastly outnumbered by a mob estimated to number more than 50.” - Deseret News